ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
581 
An examination of the blood of the frog and various other Vertebrates 
by this method showed that the thrombocytes in Ichthyopsida and 
Sauropsida are special morphological elements of the blood, and that they 
are homologous in the two groups. The blood-plates of mammals, on 
the other hand, exhibit a quite different structure, and are not homo- 
logous with thrombocytes. Thrombocytes display some resemblance to 
erythroblasts, but can be distinguished from these by the characters of 
their nuclei and cytoplasm, and by their physiological peculiarities. 
The thrombocytes never become converted into red corpuscles, and pro- 
bably arise from leucocytes by a special process of evolution. Through- 
out their life they retain the centrosome. In reference to their blood, 
Vertebrates can be divided into three classes, — the Cyclostomes, which 
possess granular erythrocytes and thrombocytoid leucocytes, the Ichthy- 
opsida and Sauropsida, which possess nucleated annular erythrocytes and 
thrombocytes, and the Mammalia, which possess annular non-nucleated 
erythrocytes and blood-plates. 
Blood of Fishes.* — Herr Bernard Rawitz has applied Ehrlich’s im- 
proved methods to the study of the blood-corpuscles of various fishes. 
He finds that in the case of fishes the blood should not be dried over a 
spirit-lamp, as in the case of mammals, but in a thermostat at a tem- 
perature of between 60° and 70°. The present paper is based upon 
results obtained from Scyllium catulus, but the author has also investi- 
gated various Ganoids and Teleosteans. He finds that Ehrlich’s method 
gives much more complicated results in the case of fishes than in the 
case of mammals and Amphibians. In Scyllium the blood contains two 
kinds of erythrocyte, one kind oval and the other round ; the latter 
arise in the blood from the former. Further, the change of shape is but 
a prelude to the degeneration of the corpuscle, which undergoes plasmo- 
lysis and karyolysis in the circulating blood. By the Ehrlich method it 
was found possible to distinguish no less than six varieties of leucocyte. 
But while there was no evidence that the erythrocytes undergo division 
in the blood, there is clear proof that many of the kinds of leucocyte 
originate in the blood stream. The circulating blood of the adult 
Selachian is therefore remarkable, because in it erythrocytes undergo 
degeneration and leucocytes multiply. The attempt to apply Ehrlich’s 
granule method to the leucocytes yielded very contradictory results, 
inasmuch as both neutrophil and acidophil granulations occurred in the 
same form of leucocyte ; and in the same preparation the granules of the 
same kind of leucocyte sometimes showed different reactions. This is in 
striking contrast to the constancy displayed by preparations of mam- 
malian blood. 
Structure of Herbert’s Corpuscles.f — Prof. A. S. Dogiel has investi- 
gated the nerve-endings of the palate of the duck and goose. He finds 
that the cells covering the tunics of Herbert’s corpuscles are not endo- 
thelial cells, but are homologous with flattened connective-tissue cells, 
and are furnished with branching processes. The axis-cylinder of the 
corpuscles consists of an axial fibre composed of many minute fibrils and 
a thick homogeneous peripheral sheath, which surrounds the fibre and 
* Arch. Mikr. Anat., liv. (1899) pp. 481-513 (1 pi.). 
f Zeitschr. f. wiss. Zool., lxvi. (1899) pp. 358-76 (2 pis.). 
