ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
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shaped cells, which invests the cavity with its duct-liko outgrowths and 
adjoining flagellated chambers, which often extend as far as the inner- 
most layer. This last consists of a cell containing still unused yolk, of 
a connective substance or mesogloea, in which there are cells and silico- 
blasts with their spicules. The larva becomes attached by the pole of 
its cavity, and undergoes an extraordinary amount of flattening ; at tlio 
same time the cylindrical cells of the ectoderm become more and more 
flattened, while the cells of the marginal part become amoeboid. As 
soon as the larva is flattened the flagellated chambers come near the 
surface, and the afferent orifices are formed by the ingrowth of the 
ectoderm-cells. The efferent system arises by the secondary breaking 
through of the primitive cavity to the exterior, while the subdermal 
cavities and the ducts which lead to the chambers are formed by later 
processes of growth. 
Protozoa. 
Parasites of the Blood of Birds and Tortoises.* — Herr B. Dani- 
lewsky has collected some of his observations on Haematozoa in two 
memoirs f on the comparative “ parasitology ” of the blood. Among 
birds, only the Passeres and the Raptores are known to be infected. 
In the red blood-corpuscles of owls Danilewsky detected Polimitus 
sanguinis avium , and saw it emerge equipped with several cilia from 
within the cells, though, like Pfeiffer, he regards this emergence as a 
result of the artificial conditions of his microscopic preparation. Fresh 
blood contains small spiral protoplasmic structures, which the author 
believes to be separated cilia of Polymitus, and it is possible that similar 
bodies in the blood of malarial patients, and even the Spirochseta 
Obermeieri of recurrent fever, may have a similar origin. Another 
curious form is Trypanosoma sanguinis avium, which, like Biitschli’s 
Rliizomastigina, has the long flagellum of a Flagellate and the undulating 
contour of a Rhizopod. It divides longitudinally or transversely, or, 
rounding itself off, segments like an ovum into thirty-two coherent cells, 
which acquire flagella and then go apart. Though it is probable that 
this form may disturb the capillary circulation, and though others 
destroy the corpuscles, decisively morbid symptoms have not been 
detected in the host, thanks perhaps to the high temperature or to the 
inoculating influence of the constant presence of these parasites for 
generation after generation. 
In the blood of tortoises the author describes a species of the flagellate 
genus Hexamitus, which probably passes from the food-canal to other 
parts of the body. The rest of the second memoir is occupied with an 
account of Hsemogregarina , which lives in the blood-corpuscles of Emys. 
It grows and forms spores, which burst into the fluid of the blood and 
probably find their way into the haematoblasts. But the origin and 
complete history of this parasite are still obscure. 
Dinobryon. J— Dr. 0. E. Imhof gives a summary account of what is 
known as to this genus of the Flagellata, ten species of which have been 
described ; all of these are from Europe. Further forms will probably 
* Biol. Centralbl., x. (1890) pp. 396-403. 
f ‘ La Parasitologie comparee du Sang,’ i. et ii., Kharkoff, 1889. 
% Zool. Anzeig., xiii. (1890) pp. 483-8. 
