202 Zoological Society. 
corpuscles, the Hyzna* would be arranged with the Canide, Basaris 
with the Urside, and Cercoleptes with the Viverride. It is curious 
that the Fox has slightly smaller corpuscles than the Dog. In the 
Ruminants the smallest corpuscles are found ; yet some of the largest. 
species have corpuscles larger than those of many Carnivora, and of 
the Horse. ‘The Camelide are the only mammals with oval blood- 
discs, like those of the lower Vertebrata in shape, but uniformly 
smaller; and in structure the corpuscle of the Camels is exactly the 
same as the corpuscle of other Mammalia, being destitute of a nu- 
cleus corresponding to that which is so obvious in the corpuscle of 
lower animals. Among the Rodents, the corpuscles of the Capybara 
are as large or slightly larger than those of Man; the Harvest Mouse 
has smaller corpuscles than any other Rodent, and in the order 
generally their size is about the same as in the Lemurs. Of the Eden- 
tata, the Two-toed Sloth has the largest corpuscles, after those of the 
Elephant, of any mammal ; those of the Armadillo are about the same 
in size as those of the Monkeys. The corpuscles of the Marsupiata 
agree generally in form and size with the corpuscles of the corre- 
sponding placental mammals. In the Monotremata, according to 
the observations of Dr. Davy, Dr. Hobson, and Dr. E. Bedford, the 
corpuscles are of the same form and about the same size as in Man. 
An examination which I made of the corpuscles of the Echidna was 
tothe same effect, but I had not an opportunity of applying a micro- 
meter to them. 
Ovirarous VERTEBRATA. 
In birds and reptiles, with a few exceptions, the corpuscles are 
oval, the long diameter being commonly rather less than twice the 
short diameter. These proportions used to be considered as univer- 
sal, but they are not so; for the long diameter of the corpuscles of 
birds and reptiles may either be nearly thrice or scarcely one and a 
half of the short diameter ; and it is remarkable that these differences 
of form are occasionally presented in the corpuscles of nearly allied 
genera. In osseous fishes, as Professor Wagner has noticed, the 
corpuscles are generally not much longer than broad; I commonly 
found a few among them of a circular shape, and he observed the 
majority of them of this figure in the blood of the Cyclostomes. In 
some species of other orders the corpuscles are about twice the length 
of their breadth; in the Pike they are somewhat angular and pointed 
at the ends; and on the whole the corpuscles of fishes are extremely 
variable in shape. The diameter of the circular corpuscles of mam- 
mals is very frequently about the same as the short diameter of birds’ 
corpuscles. They are largest in the Amphibia generally ; and largest 
of all in the Amphibia with permanent gills, as discovered some years 
ago by Professor Wagner. My measurements of the corpuscles of 
the Siren agree with his view. 
Nucleus.—This exists permanently in the blood-corpuscle of the 
lower Vertebrata, but only for a short time in that of mammals, not 
* Tt is remarkable that the extent of the streaked muscular fibre of the gullet 
of the Hyzena is the same as in the Viverride, which differ in this respect from 
the Canidae, and still more from the Urside. It would be interesting to examine 
the cesophageal muscular sheath of the Kinkajou. 
