bluuebunny/crossref_metadata_2025 huggingface dataset:
The segmental origin of the appendages of the head and anterior body segments of a spiroboloid milliped, Narceus annularis
Authors: Bodine Martha Weiss
Published: February 2005

Study of a series of embryos showed that the spiroboloid leg arrangement (1 pair of legs on each of the first 5 segments) is derived from the typical leg arrangement (no legs on segment 1, 1 pair on segments 2 through 4, and 2 pairs on segment 5) by a shifting forward one segment of the first four pairs of legs.

A careful re‐examination of the literature, especially papers by Robinson ('07), Silvestri ('03, '49), Pflugfelder ('32), and Manton ('61), combined with observations of Narceus embryos led to the conclusion that (1) the anterior body segments are primatively single (2) the gnathochilarium is composed of only one pair of mouthparts, the diplopod head having but two gnathal segments, and (3) the intercalary segment is present in the Diplopoda.
Studies on the fine structure of spermatids and spermatozoa of the crab, Pinnixia sp.
Authors: Reger James F.
Published: February 2005

Early spermatids of the carb, Pinnixia sp., are characterized by a large nuclear/cytoplasmic ratio. During early spermiogenesis an organelle, composed of pentalaminar membranes derived from the endoplasmic reticulum and nuclear membranes, is formed. Portions of this organelle become incorporated within a cylinder‐shaped invagination of the acrosome. Portions of the nuclear membrane disappear beneath the acrosome resulting in intermingling of nucleoplasm, centrioles and mitochondria. The nuclear membrane elsewhere is found as a pentalaminar membrane underlying the plasma membrane. Centrioles are found in mature spermatozoa at the base of the cylinder‐shaped acrosomal invagination, and mitochondria are found intermingled with nuclear remanants surrounding the acrosome. This datum is compared to previously described events in spermiogenesis of other decapod crustacea and arthropods exhibiting similar modes of spermiogenesis. It is concluded that the differences and/or similarities exhibited by centrioles and mitochondria in these forms could be significant in terms of subsequent zygote differentiation.
Chick lens differentiation in vitro
Authors: Katoh Arthur , Breverman Max
Published: February 2005

If that portion of a chick embryo destined to form the eye, the lens, part of the brain and the surrounding head region be removed from the chick before the lens has begun to develop, and placed in a liquid culture medium for four days, a structure resembling the lens will form in appropriate proximity to the presumptive retina, and the cells of the lens will synthesize proteins unique to and characteristic of the lens. The time course of morphological development of such explants is here described.

In vitro the lens placode dose not invaginate to form a lens vesicle, as it does in ovo. Instead placode cells elongate directly to form fibre cells. The shape of the lens formed in this aberrant manner is remarkably similar to that of normal lens.

At least one, and probably all three, of the characteristic crystallins of the lens form in these aberrant lenses, the cytological and biochemical differentiation of which proceeds normally, despite failure of the normal morphogenetic activities of the organ.
The lizard ear: Scincidae
Authors: Wever Ernest Glen
Published: February 2005

Observations on inner ear structure were made in five species of Scincidae, together with measurements of auditory sensitivity in terms of cochlear potentials. The basilar membrane and auditory papilla show a characteristic form, with considerable uniformity in dimensions except for a moderate expansion in the dorsal region and a more prominent one at the ventral end.

A characteristic feature is the presence of a tectorial membrane that covers a large part of the surface of the medial limbus, but never leaves this surface and thus fails to make any contact with the auditory papilla. Hair‐cell stimulation is achieved entirely through operation of the inertia principle (or equivalent principles) by means of a chain of sallets extending along most of the cochlea but giving way in the region of the ventral expansion to a single large body, the culmen papillae.

The sensitivity varies in the five skinks studied from better than average to some‐what below average in comparison with other lizard species. Thus an inertial (or inertia‐like) system of hair‐cell stimulation compares favorably with the tectorial membrane (restraint) system exhibited in the ears of most other lizards and all the higher animals.
Chemosensitive hairs in spiders
Authors: Foelix Rainer F.
Published: February 2005

Spiders possess curved, blunt‐tipped hairs on all legs and palps, which differ in many details from the straight, sharp‐pointed, tactile hairs: (1) the blunt tip is open to the outside, which can be demonstrated by high resolution microscopy and by the penetration of dyes; (2) the hair shaft has a double lumen which consists of a circular (tube) and a crescent shaped lumen; (3) this hair is innervated by two to three bipolar neurons whose dendrites enter the small tube, where they arborize into 16–20 branches. Multiple innervation and an open tip give strong evidence for a chemoreceptive function. Concluding from their position and distribution on the distal leg parts, a contact chemoreception is tentatively proposed. This interpretation is supported by the close structural analogy to the known contact chemoreceptors in insects. Observation of behavior indicates the importance of a contact chemoreceptor on spider legs. Other possible chemoreceptors in spiders which have been described previously by other authors are discussed.
The fine structure of coelomocytes in the annelid Enchytraeus fragmentosus
Authors: Hess Roberta T.
Published: February 2005

Two types of coelomocytes, the mucocyte and the phagocyte, occur in Enchytraeus fragmentosus. Other free cells observed within the coelomic cavity include chloragogen cells, peritoneal cells and some anucleate granular cells. Three forms of mucocytes occur and are believed to represent developmental stages. The first stage is one in which the mucous droplets are forming in the Golgi region. The second stage is a mature form, and the third stage is one in which the mucous droplets are being released. The phagocytes generally are quite large, and inclusions vary from recognizable portions of chloragogen cells to extremely small, electron‐dense cytosomes. The origin of the coelomocytes could not be determined. Probable functions of coelomocytes are discussed.
Survival of xenogeneic grafts of embryonic pigment and carapace rudiments in embryos of Chelydra serpentina
Authors: Yntema C. L.
Published: February 2005

In a study of survival of embryonic grafts in turtles, Chelydra was used as host and Chrysemys and Amyda as donors. Somites and overlying ectoderm with or without adjacent neural tube were transplanted. The operations were unilateral and orthotopic. The involved the anterior portion of the carapace. In other experiments, bilateral neural crest and dorsal neural tube were transplanted orthotopically.

In experiments with Chrysemys as donor, pigment cells formed conspicuous red areas ventrally when neural crest was included in the graft. This pigment faded gradually but persisted for three or four years.

When somites and adjacent ectoderm of Chrysemys carapace were transplanted, the graft area was lightly pigmented at hatching. This pigmentation increased subsequently. The Chrysemys grafts were either accepted or partially rejected. In cases of apparent complete acceptance, the graft region took on characteristics of the host.

When Amyda served as donor of carapace rudiments, the graft area retained characteristics of the donor. At hatching, dark spots on a yellow background were present and scutes were absent. A few months after hatching, the graft area became necrotic. Subsequently, scutes with host characteristics or skin covered the graft area.
Tooth development in Latimeria chalumnae (Smith)
Authors: Grady John E.
Published: February 2005

Tooth development in Latimeria was studied with the use of light microscopy, polarized light microscopy and microradiography.

Teeth develop from cells derived directly from the basal layer of the oral epithelium in areas where teeth have been shed or are being resorbed. The teeth are composed of true enamel, orthodentine and pulp tissues. Attachment is accom‐plished by bony attachment ankylosing the teeth to the basal bone of dental plates. The histologic picture of Latimeria teeth resembles more closely the teeth of tetrapods than those of most bony fish.
A cytologic analysis of the bag cell control of egg laying in Aplysia
Authors: Coggeshall Richard E.
Published: February 2005

A fine structural analysis of the ovotestis in Aplysia was undertaken in order to analyze the site of action of the bag cell hormone. Five stages of oocyte development are described. Of particular interest is the fact that the yolk seems to be synthesized primarily by the granular endoplasmic reticulum. In addition, small muscle cells whose long, thin processes surround the follicle of the ovotestis have been pointed out. This paper suggests that bag cell extract has a direct action on these small muscle cells causing them to contract and thus expel oocytes from the ovotestis. The evidence for this suggestion is that (1) these muscle cells are the most obvious effector cells in the ovotestis, (2) there are no signs of neural innervation of these muscles, (3) the time course for the liberation of the oocytes is so short that any other method of oocyte release is unlikely, (4) there is no cytologic evidence for any other expulsion process except muscular contraction, and (5) the ripe oocytes are attached to other cells of the wall of the ovotestis only by very small, simple junctions, thus making them the most likely cells to be expelled by muscular contraction.
The venous system of the head and neck of the opossum (Didelphis virginiana)
Authors: Dom Richard , Fisher Barry L. , Martin George F.
Published: February 2005

The venous system of the head and neck of the opossum, Didelphis virginiana, was studied by injecting the veins with a tinctorial mass. Gross dissection spechmens injected with a colored gelatin solution and corrosion specimens prepared by Batson's technique (Batson, '55) were utilized to describe the venous pattern in greater detail than is presently available in the literature. The venous drainage of the superficial structures of the head is principally by way of the V. jugularis externa and its tributaries. Although small emissary veins connect the Sinus cavernosus with the Plexus pterygoideus and the V. maxillaris, the dural venous sinuses drain primarily into the Plexus vertebralis internus and into the V. maxillaris by way of the V. emissaria foraminis retroarticularis. The small V. jugularis interna receives minor connections from the Plexus pterygoideus, the Sinus cavernosus and the Sinus petrosus ventralis as well as anastomotic tributaries from the Plexus vertebralis and the plexus of veins around the hyoid bone. However, the V. jugularis interna serves mainly as a pathway for venous drainage from the deeper structures of the neck and only minimally for draining the brain.
The endodermal nerve net of Scyphozoa
Authors: Passano Kari N. , Passano L. M.
Published: February 2005

The endodermal nerve nets of the scyphozoan jellyfish Phacellophora camtschatica and Cyanea capillata were stained with methylene blue. Small animals (3–7.5 cm in diameter) stained easily. The endodermal nerve net of both species is a synaptic net consisting of bipolar and some few tripolar nerve cells with unbranched neurites. The neurites terminate on other neurites. Very few free nerve endings were observed. The neurites have a diameter of 1/4‐1/2 μ and there is no indication of the presence of neurites too fine to be followed in the light microscope.

The gross appearance of the net changes with the size of the medusa. Staining 15–53 cm diameter animals showed that the nerve cells increase in size with the size of the animals, that the density of the nerve net decreases.

The endodermal nerve net is very similar to our interpretation of the Diffuse Nerve Net of the ectoderm but without the typical primary sense cells. In both cases the appearance of branching neurites is interpreted as an artifact caused by neurites terminating on other neurites.
Reproduction and the mechanism of meiotic restitution in the parthenogenetic lizard Cnemidophorus uniparens
Authors: Cuellar Orlando
Published: February 2005

Gross details of the reproductive cycle and the cytology of oogenesis were studied in 155 egg clutches produced by 69 captive individuals of the triploid parthenogenetic lizard Cnemidophorus uniparens. The mean clutch cycle lasted 23 days. The mean number of ova per clutch was 3.3, and the mean number of oocytes per right and left ovaries was 1.65 and 1.70, respectively. Comparison of the size of the oocytes at ovulation (9–10 mm) with the estimated mean duration of vitellogenesis (8.8 days) gave an average of approximately 1 mm yolk deposition per day. The mean time for the retention of eggs in the oviducts was 9.3 days. The germinal disc of the oocyte consists of a series of layers formed by the arrangement of various cytoplasmic and yolk particles in the polar region. In a mature oocyte the germinal vesicle is located immediately below the vitelline membrane and lies at the center of the germinal disc. The germinal vesicle is characterized by a dense disc‐like cluster of diplotene chromosomes. Diplonema extends until near ovulation when the oocytes have attained a size of about 9 mm. Diakinesis and metaphase I occur rapidly and immediately prior to ovulation. Counts of approximately as many bivalents as there are somatic chromosomes were obtained from oocytes at diakinesis and metaphase I.

The second division occurs almost immediately before or at the precise moment of ovulation. The chromosomes of the first polar body consist of dyads, of which there are as many as the triploid number of 69. A metaphase II plate obtained in polar view also revealed dyad chromosomes, of which there were approximately as many as the triploid somatic number. The second telophase is normal as evidenced by formation of the second polar body. Chromosomes from the opposing telophase plates show a monad structure. The presence of as many bivalents in the first division as the triploid somatic number of 69 indicates that the 3N condition of C. uniparens was doubled prior to meiosis. This is further supported by the occurrence of two maturation divisions each giving rise to a polar body, by the dyad structure of the chromosomes in the first polar body and the second metaphase, and by the presence of monochromosomes at telophase II. Thus, parthenogenesis in these lizards is of the meiotic type. The somatic number of chromosomes is doubled early in oogenesis presumably by a premeiotic endoduplication, and the 3N level is restored by two subsequent maturation divisions.
Circumfila and other sense organs on the antenna of the sorghum midge (Diptera, Cecidomyiidae)
Authors: Slifer Eleanor H. , Sekhon Sant S.
Published: February 2005

The antennal flagellum of the male sorghum midge is about a millimeter long and may bear over 500 sense organs. These consist of (1) tactile hairs, (2) thin‐walled pegs, (3) circumfila and (4) very small pegs of unknown function. Each of the 12 subsegments of the flagellum is divided into two globular nodes and each of these is encircled by a circumfilum of from 6 to 14 loops. The circumfila are attached to the antennal surface by short stalks. The loops of the circumfila have the basic structure of thin‐walled chemoreceptors: (1) very small pores in their delicate wall and (2) a lumen filled with branches of dendrites from sensory neurons. The outer surface of the circumfilum is covered with a labyrinth of fine ridges between which the pores are located. Some evidence was obtained that the circumfila are produced in the pupa by bifurcate trichogen cells.

The flagellum of the female is shorter than that of the male and composed of 12 cylindrical subsegments. The circumfila of the female lie close to the surface to which they are attached by short stalks. Each is composed of two parts that encircle the subsegment and of two others that run lengthwise between the circles. The surface is nearly smooth, perforated by fine openings and lacks the complex pattern of ridges seen in the male. It also has more dendrite branches but, otherwise, has the same basic structure.
The migration of blood cells of the bone marrow through the sinusoidal wall
Authors: De Bruyn Peter P. H. , Michelson Sonia , Thomas Thurlo B.
Published: February 2005

Electron microscopic observations on the mechanically undisturbed guinea pig bone marrow show that the sinusoidal lining is continuous. There are neither intercellular nor intracellular apertures allowing free communication between the extravascular and intravascular compartments. A transient migration pore is only formed during the diapedetic transit of blood cells. Serial sections show that this aperture is transcellular. A functional continuity of the sinusoidal lining appears to be maintained during the diapedesis of blood cells, which is evident from the absence of a significant extravascular leakage of plasma during this process.
Fine structural studies of Johnston's organ in the tobacco hornworm moth, Manduca sexta (Johannson)
Authors: Vande Berg Jerry S.
Published: February 2005

There are approximately 650 scolopidial units in Johnston's organ of the tobacco hornworm moth, Manduca sexta. These sensory units exhibit greater complexity than noted previously (Gray, '60; Howse, '65; Uga and Kuwabara, '65; Moeck, '68; Ong, '69; Schmidt, '69).

Each scolopale is innervated by a bipolar neuron whose dendrite terminals are modified into three ciliary structures. The largest of these differentiates near the tip into a multitubular structure. The remaining two cilia are structurally similar along the entire length of the scolopale shaft. From each of their bases, a collagen‐like structure differentiates into numerous microtubules which extend proximally into individual channels of dendritic cytoplasm. A third channel, with a less developed root apparatus, was apparent for the largest cilium.

Preliminary evidence suggests a proprioceptive function for this structure rather than an auditory one.
Growth of the calcareous skeleton during regeneration of spines of the sea urchin, strongylocentrotus purpuratus (stimpson): A light and scanning electron microscopic study
Authors: Heatfield Barry M.
Published: February 2005

Growth of the skeleton of regenerating spines of the sea urchin, Strongylocentrotus purpuratus, was studied with the light and scanning electron microscopes during the formation of a growth ring or cycle.

Growth was initiated about three days after fracture and was linear between 5 and about 40 days after fracture, with a mean rate of 0.16 mm/day. There‐after, a decline in growth rate was observed, being attributed to abrasion.

The new skeleton first appeared as minute, conical „micro‐spines”︁ on the fractured surface of the spine shaft initiating regeneration of the inner zone of meshwork. Subsequent growth of micro‐spines of both the developing inner zone of meshwork, and an outer zone of radiating wedges, formed a conical fenestrated skeleton on the fractured surface of the shaft. Further deposition of micro‐spines along the shaft, initially at the level of fracture, formed meshwork which gradually became solidified externally resulting in a new cycle about 60 days after fracture. In contrast, a new cycle was initiated at the milled ring in non‐fractured spines during total regeneration on bare tubercles, demonstrating that growth of spines also takes place in the absence of fracture.

Experiments conducted in vitro demonstrate that spine regeneration is not a polar phenomenon.
The pharyngeal bone musculature of the carp, Cyprinus carpio
Authors: Eastman Joseph T.
Published: February 2005

The carp, Cyprinus carpio, was found to have eight pairs of muscles inserting on the pharyngeal bones. These were the levator arcus branchialis V, retractor os pharyngeus superioris, retractor os pharyngeus inferioris, cleithropharyngeus superficialis, cleithropharyngeus profundus, coracobranchialis posterior, transversus ventralis V and subarcualis rectus communis. Complete morphological descriptions of the muscles are given along with relevant osteological information. The pharyngeal muscles function in mastication by moving the bones and their attached teeth against the chewing pad so that crushing and grinding of food occurs during occlusion. In addition, certain pharyngeal bone muscles enlarge the lumen of the posterior pharynx thereby admitting food to the region of the teeth and chewing pad. The homologies of some of these muscles are considered along with the historical details pertinent to the establishment of a suitable nomenclature for the pharyngeal bone muscles.
Spermatogenesis in Bombyx mori. II. The ultrastructure of synapsed bivalents
Authors: King Robert C. , Akai Hiromu
Published: February 2005

In Bombyx mori the male is the homogametic sex, crossing over occurs only in males, and chiasmata are observed in spermatocytes, but not in oocyte nuclei. If the assembly of synaptonemal complexes is an essential prerequisite for genetic crossing over and chiasmata formation, then the nuclei of Bombyx spermatocytes should contain synaptonemal complexes. Synaptonemal complexes were found in spermatocytes from young four instar larvae. The structure of meiotic bivalents is described using micrographs taken with 100 and 1000 KV electron microscopes. These data together with that from the literature are used to construct a three‐dimensional model of the synaptonemal complex and to suggest its method of origin and its function during crossing over.
The structure and development of the hairpencil glands in males of the queen butterfly, Danaus gilippus berenice
Authors: Pliske Thomas E. , Salpeter Miriam M.
Published: February 2005

Queen butterflies do not mate until the male has brushed the tufts of his scented, abdominal ”︁hairpencils„ over the female's head and antennae. The trichogen cells located at the base of each hairpencil are secretory. Presumably, these cells produce the sex pheromone necessary for mating. The liquid secretion must move from a central, microvillus‐lined vesicle through the cuticle of the hairs to coat numerous, free, cuticular „dust”︁ particles which adhere to the hairs' surface. The dust carries the secretion to or near the female's antennae. In the pupal stage the dust particles develop as outpocketings of the hair epicuticle. An amorphous matrix, probably protein epicuticle, is deposited in the outpocketings between the cuticulin layer and plasma membrane of the hair. Before the butterfly emerges from the pupa the matrix becomes enclosed by cuticulin, and the particles pinch off from the hair.
Morphology and evolution of the ectethmoid‐mandibular articulation in the meliphagidae (Aves)
Authors: Bock Walter J. , Morioka Hiroyuki
Published: February 2005

The ectethmoid‐mandibular articulation in Melithreptus and Manorina (Meliphagidae: Aves) consists of the dorsal mandibular process fitting into and abutting against the ventral ectethmoid fossa; it forms a brace for the mandible. This articulation in Melithreptus is a typical diarthrosis with long folded capsular walls. The mandible, thus, has two separate articulations, each with a different axis of rotation. No other genus of Meliphagidae (except Ptiloprora) or any other avian family possesses a similar feature.

The jaw and tongue musculature of Melithreptus are described. The two muscles opening the jaws are well developed, while those closing the jaws are small. The tongue muscles show no special developments.

A large maxillary gland, presumably muscus secreting, covers the ventral surface of the jaw muscles. Its duct opens into the oral cavity just behind the tip of the upper jaw. The frilled tip of the tongue rests against the duct opening.

The ectethmoid‐mandibular articulation braces the adducted mandible against dorsoposteriorly directed forces. The mandible can be held closed without a compression force exerted by the mandible on the quadrate, permitting the bird to raise its upper jaw with greater ease and less loss of force. The tongue can be protruded through the slight gap between the jaws, moving against the duct opening and thus be coated with mucus. Presumably, these birds capture insects with their sticky tongue. Hence, the ectethmoid‐mandibular articulation is an adaptation for this feeding method; it evolved independently in three genera of the Meliphagidae.

The ectethmoid‐mandibular articulation demonstrates that a bone can have two articulations with different axes of rotation, that the two articular halves can separate widely, and that articular cartilages can be flat and remain in contact over a large area. Its function suggests that the basitemporal articulation of the mandible found in many other birds has a similar function. And it demonstrates that in the evolution of the mammalian dentary‐squamosal articulation, the new hinge did not have to lie on the same rotational axis as the existing quadrate‐articular hinge.
The light and the electron microscopic studies of Peyer's patches in non germ‐free adult mice
Authors: Sobhon Prasert
Published: February 2005

Peyer's patches of conventional adult mice are studied with light and electron microscopy. Based on cellular types and distribution, each lymphoid follicle of Peyer's patch is divisible into four zones: the germinal center, the small lymphocytic, the interfollicular and the subepithelial zones. Three distinct cell types are present in the germinal center, i.e., dendritic reticular cells; tingible body macrophages; and lymphocytes which are classifiable into large, medium and small size. The medium size lymphocytes are the great majority in this zone. The small lymphocytic zones are characterized by a predominance of small lymphocytes with a few reticular cells. The subepithelial zone has a remarkable accumulation of macrophages and plasma cells. In the interfollicular zones there are predominantly small lymphocytes with considerable round macrophages and plasma cells, and this zone is permeated with several post‐capillary venules. The distinctive characteristics of small capillaries of the patches are also described.
Aspects of the circulatory system of Pollicipes polymerus J. B. Sowerby (Cirripedia: Thoracica)
Authors: Burnett Bryan R.
Published: February 2005

The circulatory system of Pollicipes polymerus exhibits a high degree of organization which precludes it from being referred to as an open system. The system is arbitrarily divided into four parts: (1) the circulation of the peduncle and mantle; (2) the distributive circulation of the body, which provides hemolymph to most of the cephalic gut, to the maxillary gland, and to the cirri; (3) the peripheral circulation which distributes blood from the cirri to the peripheral areas of the thoracic region, to most of the thoracic gut, and from the scutal sinus to the peripheral areas of the cephalic region; and (4) the collecting circulation, which conveys hemolymph mostly from the peripheral circulation of the body to the peduncle. There also may be a circulation that is comparable to the vertebrate lymphatic system.

Pumping of hemolymph can be attributed to three pairs of skeletal muscles that compress the dorsolateral channels. These muscles are unique for crustacean muscles in that they do not appear to be striated.

The rostral vessel appears to be a vestige of a heart in which the pump muscles have been lost. There is a similarity of the rostral vessel to the heart of Calanus finmarchicus (a copepod). This is additional evidence linking the cirripeds with the copepods within the Maxillopoda.

Electron microscope observations of the walls of the midsagittal vessels indicate that there is a more or less random layering of cellular and noncellular elements within the wall. Muscle cells appear to be incorporated in the vessel wall.
Ultrastructural contributions to the identification of cell types in the lizard epidermal generation
Authors: Maderson P. F. A. , Flaxman B. A. , Roth S. I. , Szabo G.
Published: February 2005

The ultrastructure of the epidermis at different stages of the shedding cycle has been studied in Anolis carolinensis. Cells of the germinal layer are morphologically similar at all stages in the cycle. Immediately after leaving the germinal layer all daughter cells resemble one another closely. However, they later acquire specific ultrastructural features that enable them to be classified into six distinct fully differentiated types corresponding to the grouping previously set forth by light microscopy. A comparison of cytoplasmic filament size with the known X‐ray diffraction data suggests that the Oberhautchen and β‐layer contain a protein similar to that of avian feather; the protein in the α‐layer and lacunar tissue is similar to that in mammalian hair, and the mesos layer cells probably contain a mixture of feather and hair‐like proteins. The nature of the amorphous cytoplasmic material in the mature clear layer is as yet unknown.
The early development of substrate‐brooding cichlids (Teleostei: Cichlidae) with a discussion of a new system of staging
Authors: Jones A. J.
Published: February 2005

The early development of five species of substrate‐brooding cichlid (Aequidens pulcher; Cichlasoma bimaculatum; C. biocellatum; C. nigrofasciatumandHemichromis bimaculatus) is described. Heterochrony in these species renders the standard system of staging inadequate for comparative study. A new system is proposed in which the period of development is resolved into five overlapping phases, each phase corresponding to a dissociable ontogenetic process. This form of staging permits comparison in a way which neither obscures the basic uniformity of cichlid development nor masks the differences between the species.

Two special features are discussed: the universal presence in substrate‐brooding cichlids of three pairs of embryonic adhesive organs; and the apparent presence of non‐neural crest pigment on the embryos and alevins.
Tail regeneration following autotomy in the adult salamander Desmognathus fuscus
Authors: Mufti Shahzad A. , Simpson S. B.
Published: February 2005

Tail regeneration occurs following autotomy of the tail in the salamander Desmognathus fuscus. Studies based on histology and autoradiography suggest that the cells of the regeneration blastema arise from the connective tissue of the tail stump. Following autotomy of the tail in Desmognathus the muscle of the regenerate is not derived from de differentiated or modulated striated muscle fibers of the autotomy stump. Possible sources of myogenic cells are discussed.
Effects of ovariectomy and steroid replacement on the genital tract of the viviparous lizard, Xantusia vigilis
Authors: Yaron Z.
Published: February 2005

Two glandular components are described in the genital tract of Xantusia: tubal glands in the Fallopian tube and goblet cells in the uterine villi. Sperm or seminal receptacles occur between adjacent villi in the uterus.

Forty ovariectomized lizards carrying a silk loop in the wall of the left uterus were treated for two weeks with either progesterone, estradiol‐17 β, progesterone plus estradiol or vehicle. Uteri with loops serving as a local irritant, did not differ significantly from the contra‐lateral uteri in any group, hence a response similar to the deciduomal reaction of mammals is not found in this lizard.

The weight of the genital tract is similar in sham‐operated and in ovariectomized lizards injected with either progesterone or the vehicle. Maximal increase in weight of the tract is noted with estradiol treatment, while simultaneous administration of both steroids is followed by a moderate increase of oviducal weight. Tubal glands and sperm receptacles in ovariectomized lizards injected with either the vehicle or progesterone are smaller than those of the sham‐operated or ovariectomized lizards treated with estradiol or with estradiol plus progesterone. Goblet cells are small and lack secretory granules in ovariectomized lizards injected with either the vehicle, or with estrogen or progesterone alone. Both steroids, given together, restore the size and apparent secretory activity of the goblet cells. It is concluded that in this viviparous species, both estrogen(s) and progestin(s) are essential for the maturation of the genital tract in the preovulatory stage.
Macrophage activity in wolffian lens regeneration
Authors: Yamada T. , Dumont James N.
Published: February 2005

The cell type mainly involved in the phagocytic uptake of melanosomes from iris epithelial cells during Wolffian lens regeneration in the adult newt is identified on the basis of electron and light microscopic evidence as a macrophage of monocytic origin. Appearance of macrophages in iris and ciliary epithelia following lentectomy is a part of leucocytic infiltration of the area, in which granulocytes, mast cells, and other cell types also participate. The general pattern of leucocytic infiltration was studied as a function of time after lentectomy. Infiltration of the iris epithelium by macrophages is reduced when most of the melanosomes have been removed from the cytoplasm of the epithelial cells and finally ceases when depigmentation has been completed. The possibility that an immune mechanism mediated by macrophages is involved in dedifferentiation of iris epithelial cells is discussed.
Mastication in the little brown bat, Myotis lucifugus
Authors: Kallen Frank C. , Gans Carl
Published: February 2005

The masticatory apparatus of the vespertilionid bat Myotis lucifugus appears generalized. Principal modifications for more efficient trituration have involved accessory tooth cusps. Chewing strokes pass through orbits (up to 7/sec) involving translations along and rotation about three axes. Direction of chewing typically reverses by at least the fifth or sixth consecutive orbit. Reversal involves modification of the downstroke at varying positions along its course. Compared to certain other bats, which do not utilize oral phonation for echolocation, Myotis chews much more rapidly, with many more degrees of freedom in orbital configuration. The overall envelope of motion is remarkably similar in all these species. The jaw muscles of Myotis act asymetrically, and in more than one direction as the orbit progresses. They overlap in their periods of activity forming a continually‐modified muscular sling. Unilateral force couples facilitate orthal rotation at the condyles and movements of them. Bilateral couples, pitting protrusors of one side against retrusors of the other, facilitate lateral translation. The pterygoids are instrumental in continuing motion across the top and bottom of the orbit. Countercontractions are particularly important in stabilizing and protecting the temporomandibular joints. The mandibular symphyseal joint appears to act passively, providing additional flexibility for the system. Higher nervous control beyond the simple jaw‐opening reflex appears necessary to explain the firing order of the digastrics and the phase relationship of orbital reversal to overall muscular firing intensity. Control mechanisms, ancillary phenomena and comparative aspects are discussed.
Secretion by ependymal cells of the neurohypophysis and saccus vasculosus of Polypterus ornatipinnis (osteichthyes)
Authors: Marquet Eugene , Sobel Harold John , Schwarz Ruth , Weiss Martin
Published: February 2005

Electron microscopic studies of the neurohypophysis and saccus vasculosus of the bichir (Polypterus ornatipinnis) reveal an apocrine release of secretory material by ependymal cells (e.g., crown cells). The secretory material appears to migrate along the microtubular apparatus and the ciliary filaments to the cell buds. It is postulated that the formation of the buds and their release is mediated by cilial action. Secretion buds are noted in the cerebrospinal fluid and vascular sinusoids.

Bulbous projections of neurohypophyseal secretory tracts extend into the ependymal lumen which also contains elementary secretion granules. Specialized “liquorkontaktneurone” are interspersed with ependymal cells.

An interrelation between the hypothalamus, neurohypophysis, saccus vasculosus, and the meta‐adenohypophysis is postulated.
The relationship of early oocytes to putative neoblasts in the serpulid Spirorbis borealis
Authors: Potswald Herbert E.
Published: February 2005

The fine structure of the ovary in the serpulid Spirorbis borealis has been described. The ovarian wall consists of from one to several layers of peritoneal cells. Peritoneal cell processes extend deep into the ovary and may be seen between developing oocytes. Although young oocytes may also be in close apposition to one another, intercellular bridges have not been observed. When primary oocytes at the surface of the ovary reach a diameter of about 20 μ, they start to erupt into the coelom. Ovulation results from a simple separation of overlying peritoneal cells which lack specialized cell‐to‐cell contacts. Once a free surface of an ovulating oocyte is exposed to the coelom, microvilli and primary coat develop. Previtellogenic coelomic oocytes are often observed in close proximity to putative neoblasts (perivasal cells), which suggests a possible functional relationship. The confusion that extists between germ cells, peritoneal cells, and so‐called neoblasts in polychaetes is discussed.
A new model for the structure of the centriolar satellite complex in spermatozoa
Authors: Summers Robert G.
Published: February 2005

The ultrastructure of the centriolar satellite complex in the spermatozoon of the hydroid, Pennaria, is presented. The complex consists of nine spoke‐like arms which emanate from the distal centriole and of nine wedgeshaped connectives which extend into the flagellum joining each of the alpha doublets and the flagellar plasmalemma. Based upon these observations a new model for the structure of the centriolar satellite complex is proposed. In addition, similar centriolar satellite complexes are reported in the spermatozoa of two echinoderms, Ctenodiscus crispatus and Thyone briareus, in support of the proposed model.
The anatomy and histology of the nasal cavities and the nasal salt gland in four species of fringed‐toed lizards, Acanthodactylus (Lacertidae)
Authors: Duvdevani Israel
Published: February 2005

The anatomy of the nasal cavities and lateral nasal gland (functioning as a salt gland) are similar in the four species of Acanthodactylus studies. Nasal cavities are not histologically different from those of other squamates. The vestibule is covered with a multilayered, stratified, squamous epithelium. The nasal gland is situated in the conchal space, lateral to the principal cavity and the vestibule. It is a tubular branched gland, highly vascularized. Innervation is derived from the N. trigeminus and was observed to reach only the anterior, small portion of the gland. The collecting duct opens to the vestibule, anterior to its connection to the principal cavity. Secretion of the nasal salt gland probably collects in lower anterior part of the vestibule. From there, liquid can either dry out while moistening the inspired air or be blown out by “sneezing.” Histological differences were observed between a non‐active and an active salt gland.
A cytological study of the ovary of Rhodnius prolixus. II. Oocyte differentiation
Authors: Huebner Erwin , Anderson Everett
Published: February 2005

This investigation presents the ultrastructural changes that occur during previtellogenic and vitellogenic growth of the oocyte of a telotrophic ovary. The ovarioles of a newly emerged adult Rhodnius have their full complement of oocytes located at the base of the tropharium. These oocytes are in cytoplasmic continuity with the syncytial tropharium via trophic cords. The nuclei of these oocytes are in prophase of meiosis I with condensed chromosoes; synaptonemal complexes are visible in many. During oocyte growth the nucleus or germinal vesicle enlarges from a 3–4 μ diameter to a 45–50 μ diameter and the chromosomes become diffuse and arrested in late prophase I. Small previtellogenic oocytes are limited by a morphologically unspecialized oolemma and contain a pair of centrioles, rough endoplasmic reticulum, a few small Golgi complexes and clusters of mitochondria. By the end of previtellogenesis there has been an increase in the volume of the oocyte due to the transport of ribosomes and mitochondria into the oocyte from the tropharium. During vitellogenesis the oolemma develops a microvillous border and yolk precursors are internalized by pinocytosis. Small stacks of annulate lamellae, numerous ribosomes and the other organelles are restricted to the thin layer of cortical ooplasm; the lipid protein‐carbohydrate yolk spheres and glycogen are located centrally. In oocytes not stimulated, autolysis occurs as dense local areas within the ooplasm.
The anatomy, physiology, functional significance and evolution of specialized hearing organs of gerbilline rodents
Authors: Lay Douglas M.
Published: February 2005

Middle and inner ear anatomy correlates with neurophysiological responses to a wide range of sound frequencies for species of the Gerbillinae representing generalized, intermediate, and specialized anatomical conditions. Neurophysiological data were recorded from 81 specimens of 13 species representing six genera. Anatomical parameters involved in the process of hearing were correlated with the neurophysiological data to assess the effects of different degrees of anatomical specialization on hearing. The 13 species tested in this manner have graphic curves of auditory sensitivity of remarkably similar disposition over the frequencies tested and to those published for Kangaroo Rats. Ears with anatomical specializations show greater auditory sensitivity.

The natural history of the Gerbillinae, particularly the kinds of predators, degree of predation, and habitat is reviewed and utilized to interpret the significance of the degree of auditory specialization in the forms studied and to evaluate the prevailing hypothesis that these specializations enhance the ability of these rodents to survive in open desert situations by detecting and evading predators.

The middle ear anatomy of five additional genera and species was also studied. Thus, data on the entire spectrum of gerbilline middle ear morphology provide an evolutionary sequence. Certain anatomical parameters of the organ of Corti show a degree of specialization parallel to that of features of the middle ear. The morphological changes and possible functional roles of these features are considered.

A very high correlation exists for degree of specialization and aridity of habitat, thus specialization increases with increasing aridity. This increased specialization may result from more effective predation in open xeric environments. Auditory acuity for a wide range of low frequency sounds augmented by auditory specialization is hence more advantageous here. There does not appear to be selection for hearing at particular frequencies in this range. The peaks of greatest auditory sensitivity appear to correspond to the resonant frequencies of the different components of the middle ear transformer and cavity.
Embryology of the sheep. II. The alimentary tract and associated glands
Authors: Bryden M. M. , Evans Howard E. , Binns Wayne
Published: February 2005

The day‐by‐day development of the alimentary system of the sheep embryo from 14 to 34 days is documented and described. This includes development of the mouth, the pharynx and its derivatives, esophagus, stomach, intestine, cecum, pancreas and liver.

This work provides standards within the normal range of development of the ovine alimentary system on which studies of abnormal development can be based.
Lymphoid tissue in the snapping turtle, Chelydra serpentina
Authors: Borysenko M. , Cooper E. L.
Published: February 2005

This report presents light microscopic descriptions of lymphoid organs and aggregates in the snapping turtle Chelydra serpentina. The thymus and spleen were found to be similar to those of other ectothermic vertebrates. Certain gut associated lymphoid aggregates suggest the presence of reptilian equivalents of tonsils, Peyer's patches and the avian bursa of Fabricius. Lymphoid aggregates located in the axillary and inguinal regions were apparent for the first time in an ectothermic vertebrate. These are of particular interest since they may represent ancestors of true lymph nodes in analogous locations in mammals. It is concluded that the snapping turtle is not deficient in lymphoid tissue, although there is a conspicuous absence of typical germinal centers, characteristic of mammalian organs.
Development of polarity and bilateral asymmetry in the palleal bud of Botryllus schlosseri (Pallas)
Authors: Izzard Colin S.
Published: February 2005

The development of the polarity and bilateral asymmetry of the future adult zooid has been traced to their earliest morphological expression in the palleal bud of Botryllus. The account is based upon continued observation of living buds. The polarized antero‐posterior and dorso‐ventral axes are first expressed by the skewing of a symmetrical, hemispherical bud towards the anterior end of the parental bud. Identification of these axes is reinforced by the development of a loop‐like blood circulation, the primary circulation, in the horizontal plane during the enlargement of the skewed hemisphere to form a stalked vesicle. Bilateral asymmetry is first expressed by the asymmetrical expansion of the vesicle stage. The right posterior corner of the vesicle expands further posteriorly and becomes more acute than the left posterior corner. This larger expansion persists throughout the development of the right atrial cavity, which finally expands across the mid‐line to partially surround the gut. The bilateral asymmetry, expressed in the expanded vesicle, is reinforced by the development in sequence of a rounded gut rudiment and a pericardial rudiment in positions that would be expected from the asymmetry of the expanded vesicle. The first appearance of the gut rudiment occurs earlier than had been recognized previously. Conflicting accounts of the time and mode of formation of the pericardial rudiment have been clarified. The results of this study are discussed in the context of determination of bud territory, polarity and bilateral asymmetry.