16
preservation in formalin brings out these details as well as any staining process,
yet used by me. Efforts to stain the largest coccidia have not yet been made.
The youngest coccidia appear to have a structure and staining reactions
closely similar to those described by Labbé (4) for proteosoma. I note-
especially the " coloration un peu grisâtre " with hæmato-xylin, mentioned by
him ; but I am unwilling ta speak definitely on these points without much more-
study than I have as yet been able to afford them.
4. Some Miscellaneous Observations.—The number of coccidia found in
different mosquitos fed on the same birds varies from none, or one or two, in a
few cases, to several hundreds exceptionally. The largest number counted by
me has been 445. To judge from the experiment on the three sparrows recorded
in section II, paragraph 5, their number depends on the number of parasites in-
the blood of the subject, or more probably on the number of parasites ripe for
transference to the mosquito.
No sign of movement has been ever observed in the cells.
The capsule of the coccidia is well defined from the third day. It is exten-
sible, as shown by exerting pressure on the cover glass. As already explained,
it bursts readily on the sixth day and later on the addition of water. Manson
noticed a similar fragility in water in the early " pupal " stages of filaría—a
fragility which was overcome toward the sixth day when the pupa becomes fit
for free life; and he suggests, in a letter to me, that if there arrives a stage
in the history of the coccidia when they no longer burst in this manner, it will
be a sign, as in filariæ, of a possible further life in that medium.
Are these bodies intracellular ? We should expect so from their general
structure, but I may say that no certain evidence of it has shown itself as yet
even in the youngest forms. On one occasion, however, while watching a
hyaline cell of the third day in a newly made specimen, I observed something
collapse- round it, upon which it immediately acquired a coarser contour and
shortly afterwards became vacuolated. It may be that the external " homo-
geneous " coat consists of very delicate cells, which are occupied by the
coccidia.
I have often thought that the proteosoma coecidia derived from crows,
larks and sparrows, respectively, differ in some minor particulars ; but am not-
prepared for any statement on the point.
I have often mentioned the "bright points" in the older coccidia, I think
them to be of an oily nature, because they appear to run together in preserved
specimens—just as Leukart observes in the similar objects seen in coccidium
oviforme. The resulting large drops of " oil " are shown in some of the illus-
trations, notably in Plate I, figures 21 and 22.
It is most necessary to mention that in preserved specimens, especially in
those mounted in formalin of too great a strength, the pigment undergoes a
very curious enlargement—so much so that it may almost fill the smaller cells
this is evidently some chemical alteration.
I have not had time to apply tests for pigment to the coccidia.
The nuclei of the cells of the malpighian tubes sometimes escape into the
cavity of the stomach, where they may be mistaken for coccidia of the third day,
They are, however, round, possess a marked nucleolus, and have no pigment.
I wish particularly to reiterate, in order to avoid future misunderstanding,
that there is no possible doubt as to the continuity of development from the
\ill\er pigmented to the later unpigmented forms. Apart from a generalsimilarity