bluuebunny/crossref_metadata_2025_split huggingface dataset:
The integumentary, pulmonary, and cardiac modifications correlated with increased cutaneous respiration in the amphibia: A solution of the ‘hairy frog’ problem
Authors: Noble G. K. 
Published: February 2005

AbstractAstylosternus robustus has greatly reduced lungs. All Amphibia exhibiting such a reduction have their epidermis either penetrated by capillaries or thinned to facilitate greater cutaneous respiration. The epidermis of both sexes of A. robustus is penetrated by capillaries. The «hairs» of the adult male are merely extensions of this vasculated epidermis to compensate for the greater muscularity, size, and activity of this sex.The digits of terrestrial urodeles do not serve as special centers of cutaneous respiration. Digital sinuses are present in all urodeles. The abdominal and femoral tubercles of arboreal and some terrestrial frogs may function greatly in respiration, for their epidermis is penetrated by capillaries.All urodeles and frogs having well‐developed and frequently emptied lungs possess a functionally complete auricular septum and a spiral valve. Injection experiments demonstrate a complete separation of arterial and venous blood in living specimens. A reduction of the lungs conditions a reduction of the left auricle, but disuse causes no change in size. A great decrease of the lungs, or even a disuse of them, conditions a fenestration of the auricular septum and a loss of the spiral valve. The spiral valve is formed by a backward growth of one of the synangial valves and is not homologous with the accessory valves of dipnoans. Lungless salamanders have no left auricle and no spiral valve.
External reproductive organs of the common grass spider, agelena naevia walckenaer
Authors: Petrunkevitch Alexander 
Published: February 2005

AbstractOne of the most perfect “lock and key” adaptations known, the external reproductive organs in spiders are subject to considerable variations. Two extreme types of female reproductive organs are described in detail, and these in turn compared with the European species of the same genus. Thus it is shown that the reproductive system in the same genus of spiders may exhibit great differences in structure while all other characters remain more or less the same, the natural conclusion being that caution should be exercised in creating new or splitting up old genera on the basis of characters of the external reproductive system. The same applies to the male.Two extreme types of palpi are described and then compared with the palpi of the European species. In the case of the male, however, the differences seem to be of a less profound nature.
The primordial germ cells of Hemidactylium and other amphibia
Authors: Humphrey R. R. 
Published: February 2005

AbstractThe primordial germ cells of urodeles and anurans can occupy comparable positions in the embryo only in very early stages of development, if at all. When first recognizable as reproductive elements, their situation in the two amphibian orders is quite strikingly different.The germ cells first become recognizable in urodeles in the medial edge of the lateral mesoderm; there is no evidence that their position previous to this time is other than mesodermal. In the anura they are entodermal in association during early development; they are finally separated from the dorsal portion of the roof of the archenteron to form a single axial germ‐cell cord. No amphibian species studied showed a mode of origin different from that characteristic of its order.The so‐called migration of the amphibian germ cells to their definitive situation is interpreted as the result of growth shiftings of related parts. Germ cells do not migrate independently through the tissues. Aberrant or ectopic cells for the most part result from failures or faulty correlations of growth processes. Certain aberrant cells of the caudal portion of the body in urodeles indicate the inclusion of sex elements in the ventral as well as in the lateral mesoderm.
Modification of development on the basis of differential susceptibility to radiation I. Fundulus heteroclitus and ultraviolet radiation
Authors: Hinrichs Marie A. 
Published: February 2005

AbstractThis paper reports experiments with Fundulus heteroclitus to modify larval development by means of ultraviolet radiation. Eggs were exposed to radiation at various intervals after fertilization for varying periods of time. The results accord with previous work on fish teratology, and the developmental types obtained are essentially similar to those produced by chemicals, cold, and hybridization. The deviations from normal development occur in the same body regions as do those in other vertebrates whose early development has been modified by the action of radiation (x‐rays, radium, etc.).The results of these experiments indicate that there is a non‐specificity in susceptibility relations with the production of similar types of monsters for widely different reagents. That these eggs are differentially susceptible to the action of ultraviolet radiation is indicated by the fact that those regions which have the highest metabolic activity when an inhibiting influence is active are the ones most generally affected. Thus modifications of the nervous system, sense organs, circulatory system, tail region, and body axis result, respectively, in the production of varying degrees of cyclopia, inadequate circulation, short, stubby or bent, non‐motile tails (some bifid), and anterior twinning.As these modifications may be produced by applying inhibiting influences during the first few minutes after fertilization, it is evident that there is in the egg at this stage some constitutional or physiological basis which determines early differences in susceptibility of its various parts.
Egg formation in a leech
Authors: Heath Harold 
Published: February 2005

AbstractIn a leech infesting the Alaskan codfish germinal masses in the ovary proliferate secondary groups, comprising about forty cells in which a follicle and central supporting cell early differentiate. Active division results in approximately 500 cells which apparently develop ductules extending to a point on the surface of the egg. Granules of unknown origin then appear in each nurse cell, and are drawn down the ductules into the egg which can now be distinguished. Reasons are given for the belief that the nutritive material is drained from the nurse cells by amoeboid activity of the egg. In early stages the nutritive mateiral forms a loose reticulum which gradually becomes transformed into a more extensive network, persisting until the maturation divisions. In this latest period the follicle and nurse cells, which become shrunken as the ovum enlarges, usually are stripped off and soon disintegrate.
The germ cells of anurans. II. An embryological study of sex differentiation in Rana catesbeiana
Authors: Swingle W. W. 
Published: February 2005

AbstractEmbryological study of bullfrog tadpoles collected from various parts of the United States has shown the existence of local races which differ markedly in regard to the time of occurrence and character of the developmental processes involved in the formation of the definitive testis of the male individuals. Those races in which the gonads of the two sexes are easily distinguished in early larval stages are called differentiated. Other local races show a peculiar gonadic development chiefly affecting the males, the definitive testis sometimes not appearing until near the end of the second year of larval life. Such races are called undifferentiated, because the morphological features of the definitive testes are not established until late. The larvae first develop a peculiar gonad (progonad) which later degenerates and is replaced by the definitive testis. All male animals of the undifferentiated strains exhibit the gonad cycle.The progonad varies among the local frog races in regard to the length of persistence and degree of differentiation attained before undergoing degeneration. Its germ cells may exhibit a typical male maturation cycle ending in degeneration, or the cells may differentiate along both male and female lines or remain sexually neutral.The development and differentiation of the progonad in the various races are described and a detailed account given of the origin of the definitive testis. The problems of sex differentiation and continuity of the Keimbahn in anurans are discussed.
Branchiomerism and the theory of head segmentation
Authors: Kingsbury B. F. 
Published: February 2005

AbstractThe summary of this paper is as follows:
A critical review of the developmental evidence shows that the branchial pouches are formed in cephalocaudal sequence subsequently to the segmentation of the dorsal mesoderm.
The pouches interrupt a continuous sheet of mesoderm to form the branchial arches.
The arches when formed do not correspond topographically to the dorsal somites.
Branchiomerism does not therefore coincide with somitic metamerism.
The branchial structures do not support the theory of head segmentation.
The nervi trigeminus, facialis, glossopharyngeus, and vagus cannot be regarded as segmental nerves.
There is no evidence that branchial pouches or arches have been elided from the series.
The problem of meristic homology is briefly discussed.
The metabolic gradients of vertebrate embryos. II. The brook lamprey
Authors: Hyman L. H. 
Published: February 2005

AbstractDisintegration in killing agents was studied throughout development. In the unfertilized egg and cleavage stages the death gradient runs from animal to vegetal pole. In the late blastula stage the future dorsal surface and future point of gastrulation show heightened susceptibility. The gastrula has a gradient from anterior to posterior end along its dorsal surface, with a slight reverse gradient around the blastopore; lateral and ventral regions are least susceptible.Before and after the appearance of the neural groove, the dorsal surface shows increased susceptibility with gradient in it from anterior to posterior end. The neural tube is highly susceptible, with a death gradient from anterior to posterior end and a slight reverse gradient at its posterior end.During late stages and in the larva the double gradient is present; death begins at the two ends and progresses backward from head, forward from anus; from the former most rapidly. The least susceptible place is near the posterior end. The posterior reverse gradient is less developed in the lamprey than in other vertebrate embryos, due, probably, to its lack of a tail bud.Assuming that death differences indicate differences in rate of activity, it appears that such differences in activity may be causes and not results of developmental processes, for the development of certain parts (dorsal surface, blastopore, central nervous system) is indicated by heightened activity before it is evident morphologically.
The formation of the sex glands and germ cells of mammals. II. The history of the male germ cells in the albino rat
Authors: Hargitt Geo. T. 
Published: February 2005

AbstractThe testis is differentiated from the indifferent gonad in embryos of fourteen days. The indifferent gonad and the sex cords contain large and small cells, both of which are derived from the coelomic epithelium. The large cells have generally been called primordial germ cells, they increase by mitosis and reach their maximum in embryos of seventeen days. But all the large cells degenerate and have completely disappeared by nine days after birth. The large cells, therefore, do not contribute to the formation of cells in the tubules of the adult testis. After the disappearance of the large cells, the solid seminiferous tubules are composed of indifferent epithelial cells of a uniform type, which are descendants of the small cells of the genital ridge, and which later form both the germ cells and the Sertoli cells of the seminiferous tubules of the adult testis.Definitive spermatogonia begin to form fifteen days after birth, when the solid cords are becoming hollow tubules; spermatocytes occur at twenty‐three days, when the testes are entering the inguinal canals; spermatids are first observed about thirty‐three days, when the testes enter the scrotum, and perfect spermatozoa at forty‐eight days. Sertoli cells cannot be clearly distinguished until almost puberty; these cells may be only indifferent epithelial cells. During the development of the seminiferous tubules, a good many cells of all stages of spermatogenesis degenerate.
The development of the premandibular head cavities and the relations of the anterior end of the notochord in the chick and robin
Authors: Adelmann Howard B. 
Published: February 2005

AbstractThe prochordal plate in the chick is a thickening of the entoderm in the anterior part of the area pellucida. It consists at first of several layers of yolk‐charged cells, which finally lose their yolk and form a thin layer of entoderm.The prechordal plate (an area of mesodermal proliferation immediately anterior to the notochord) arises immediately anterior to the primitive streak (and head process when the latter appears) in a part of the region once occupied by the prochordal plate. Later the prechordal plate comes to lie upon the dorsal wall of the foregut.The premandibular cavities arise in condensations of the prechordal mesoderm. The cavities seem to appear during the rapid expansion of the prechordal mesoderm which occurs in response to a release from constraint imposed by surrounding structures. They are connected with one another across the midline by a usually solid bridge of mesoderm.Later, the cavities are replaced by a mesodermal condensation which serves as a mold, on the surface of which the oculomotor muscles appear, arising before the disappearance of the premandibular head cavities.Differences in the relations of notochord and hypophysis in the chick and robin may be explained by an analysis of the growth of the two forms. The analysis furnishes a basis for understanding the relations of the anterior end of the notochord in the mammal.
The structure and division of paramecium trichium stokes
Authors: Wenrich D. H. 
Published: February 2005

AbstractParamecium trichium varies from 50 μ to 105 μ long with most individuals between 80 μ and 90 μ. The width varies from one‐third to one‐half the length. It is somewhat depressed dorsoventrally. The broad buccal groove extends from the anterior left border diagonally across the ventral surface to the mouth, which is usually slightly anterior to the middle and to the right side of the median line. The mouth leads into a relatively long cytopharynx containing an undulating membrane. The cytopyge is subterminal and the small caudal tuft of longer cilia is subapical. The plastic ectosarc contains numerous trichocysts. A contractile vacuole apparatus occurs near either end. Each is deeply located and stains more intensely than surrounding protoplasm. In life there appear to be two alternately contracting vacuoles with smaller ones adjacent. Contractions are from fifteen to twenty‐five per minute. The macronucleus is medium in size and the single micronucleus is of the ‘caudatum’ type.Binary fission appears to be initiated by a metaphase‐like condition of the micronucleus. This is followed by great enlargement and the eventual separation of the chromatin threads into two anaphase groups. The metaphase thus appears to precede the changes which correspond to a prophase in other cases. During division of the body, the two old contractile vacuoles persist as the posterior ones for the daughters, new anterior ones being developed.
Freezing and survival of insects at low temperatures
Authors: Payne Nellie M. 
Published: February 2005

AbstractThe literature on the general subject of freezing and survival both in plants and in animals is briefly reviewed and a bibliography given. Insects representing three ecological groups, (1) the oak borers—exposed to temperature extremes normally; (2) stored‐products insects representing supposedly a tropical or subtropical group, and, (3) aquatic insects never exposed to temperatures lower than 0°C., were chosen for this study. Determinations of the freezing and undercooling points were made during the yearly cycle.Both the stored‐products insects and the aquatic insects studied showed no periodicity in freezing or undercooling. The oak borers showed marked periodicity. The freezing‐point varies directly with the moisture content. Cold‐hardiness was produced experimentally by, (1) exposure of insects to low temperatures and, (2) by dehydration. Loss of cold‐hardiness was produced experimentally by combinations of high temperature, food, and high relative humidity. The freezing‐point ordinarily found corresponds with that of the blood. Repeated freezings of the same insect or tissue showed no hysteresis. There exists in certain insects a secondary freezing‐point below that ordinarily found. Oak borers in summer condition die at the first freezing‐point; in fully hardened condition they die at the secondary freezingpoint.
The development of the eye muscles of the chick
Authors: Adelmann Howard B. 
Published: February 2005

AbstractThe anlage of the abducens musculature appears first at 24–25 somites as a condensation situated dorsal to the mandibular arch.The anlage of the superior oblique grows forward from a mesodermal condensation situated in the maxillomandibular region, termed for convenience the maxillomandibular condensation. This last consists of three parts: (1) the anlage of the superior oblique: (2) the anlage of the abducens musculature, and, (3) an intermediate region.The intermediate portion of the maxillomandibular mass forms a condensation with which the anlage of the abducens musculature fuses. Its fate is, therefore, similar to that of the so‐called ‘muscle E’ of elasmobranchs, which has been described as fusing with the lateral rectus. How much muscle is formed from the intermediate condensation in the chick has not been determined.The development of the pyramidalis and quadratus nictitans muscles, derivatives of the abducens complex, is described.The premandibular head cavities are replaced by solid mesodermal condensations, on the surface of which the anlagen of the oculomotor muscles appear. The premandibular mass expands laterally and anteriorly over the bulbus, carrying the oculomotor muscles to their respective positions on the bulbus.Portions of the premandibular and maxillomandibular condensations not involved in eye‐muscle formation take part in the formation of choroid and sclera.The growth shiftings of the eye muscles are analyzed. The order of their appearance is commented upon.
The effects of certain physical and chemical factors on locomotion and others life‐processes in Amoeba proteus
Authors: Hopkins D. L. 
Published: February 2005

AbstractAmoeba proteus was raised in a modified and diluted Ringer solution. When the pH of this culture medium became less than 6.0, the normal activities of the amoebae were interfered with; and when a still lower pH was attained, the amoebae died off. The same was true when the pH became greater than 8.0. At neutrality the activities were subnormal, very dark, and rounded. The rate of locomotion of amoebae raised in solutions with a pH less than 7.0 showed a maximum rate of locomotion at pH 6.6, which decreased as the pH changed in either direction, dropping to a very low rate at pH 7.0 and above and also below 6.0. For amoebae raised at a pH above 7.0 the rate was maximum at pH 7.6 and decreased as the pH changed in either direction; it was low at pH 7.0 and below and also above 8.0.On increasing the external osmotic pressure of the medium it was found that the effects caused varied somewhat with the hydrogen‐ion concentration. Small increases in osmotic pressure decreased the rate from the normal at pH 6.0 and 8.0, increased it at pH 6.6 and 7.6, and did not affect it at pH 7.0. Osmotic pressures above that produced by M/20 lactose caused locomotion to cease in a short time at all pH values.
Spiral movement in man
Authors: Schaeffer A. A. 
Published: February 2005

AbstractBlindfolded persons walk, run, swim, row, and drive automobiles in clock‐spring spiral paths of greater or less regularity when attempting a straightaway. The spirals turn either right or left in one and the same individual, and may do so even in one experiment. But either right or left turns predominate in the great majority of individuals, often to a high degree. The paths show marked individuality, and there is some ground for thinking there exists a correlation between temperamental differences and general character of path.The mechanism which produces the spiral path is not located in the locomotor organs, but in the central nervous system and is probably identical essentially with the spiral mechanism in other motile organisms, all of which move in spiral paths when there are no guiding senses to direct the path. The clock‐spring spiral in man is interpreted as the expression in two dimensions of space of a helical spiral mechanism which seems to exist in all motile organisms moving in three dimensions of space and in amebas which move in two dimensions. In a large number of lower organisms the number of body lengths per spiral turn is almost constant, being about 4.5. The smallest regular swimming spirals in man are very close to this value, but the smallest regular walking spirals are somewhat larger. The fundamental spiral mechanism seems to be of molecular dimensions, and there seems to exist a demonstrable locomotor bilateral asymmetry in very nearly, if not quite, all organisms.
A comparative study of the spermatogenesis of five species of earwigs
Authors: Morgan William Pitt 
Published: February 2005

AbstractThe following species of earwigs are used in this study: Labidura bidens, Labia minor, Anisolabis annulipes, Anisolabis maritima, and Forficula auricularia.
In all species the chromosomes are divisible into, a) autosomes and, b) XY‐complex.
The chromosome distribution in regular in Labidura bidens and Labia minor. The male diploid number is 12 and 14, respectively. Each has an XY‐complex in which the X is a single chromosome.
In both Anisolabis annulipes and Anisolabis maritima the male diploid number is 25, or 22 autosomes and an XXY‐complex. The two X components remain fused during the first spermatocyte division.
The diploid number in the male of Forficula auricularia is 25 and 24. The chromosome number is constant in the individual. The irregularity is interpreted as due to the fusion of the two X components in the individuals with 24 counts and to these X components remaining separate in the earwigs with the 25 counts.
An explanation is given for some of the variable results obtained in former studies of the chromosomes of Forficula auricularia.
The discussion considers the possible origin of the variations in chromosome numbers in the earwigs.
Observations on the gross and microscopic anatomy of the sloths (Bradypus griseus griseus Gray and Choloepus hoffmanni Peters)
Authors: Wislocki George B. 
Published: February 2005

AbstractIn this study observations are reported upon the morphological differences between the three‐toed and two‐toed forms of sloths, as well as a comparison made of some aspects between the sloths and the other groups of the Xenarthra. Much attention has been paid to the gross, as well as the histological examination of the viscera, musculature, and the vascular and lymphatic systems.The importance of the correlation of the morphological findings with physiological studies has been emphasized. For example, the probable correlation of the vascular plexuses of the extremities with the postures and muscular activity of the different members of the Xenarthra is discussed. Much new information has been gained concerning the placentation and development of the sloths, as well as concerning the structure of the male and female reproductive tracts.