1875. | RED BLOOD-CORPUSCLES. 481 
a few species longer, and in more smaller than in some of the Anura. 
Thus in most Tortoises and Croeodiles and the Slow-worm the cor- 
puscles are longer than, though not so broad as, in the Green Tree- 
Frog and in some exotic Toads, but are smaller in Python, Teius, 
Zootica, Lacerta, Plestiodon, and Iguana tuberculata than in any 
Batrachians ; and of this Iguana, which has the smallest known 
reptilian corpuscles, it is remarkable how much smaller they are than 
those of Iguana cyclura. Nor are the corpuscles in Reptiles, though 
regularly larger than in Birds and Osseous Fishes, ever quite so large 
as in Rays and Sharks; and in some Ophidians and Saurians the 
corpuscles are smaller than in certain Salmonide. There is more 
uniformity of the corpuscles throughout the class of Reptiles than in 
some single orders of Apyrenzemata; in no Reptile are the corpuscles 
twice the size of those in other reptiles, and the corpuscles are oval 
in every species. Here, again, there is a conformity of Birds to Rep- 
tiles, and a divergence of both these classes from Mammalia, each 
of those pyrenzematous groups being in these respects more like an 
order than the class of Apyreneemata. But Reptiles, unlike Birds, 
present no relation between the size of the corpuscles and that of the 
species ; they are as large in the little Viper and Snake as in the 
huge Pythons and Boa, and in the small Anguis and Chameleon as 
in the large Teiws and Monitor. Differences in the size of the cor- 
puscles probably occur at certain seasons, 
Brrps. 
Form and size of the eorpuscles. —They are oval in all birds, genes 
rally flat, with a slight tendency to be gibbous on the broad surfaces, 
altogether of much the same shape as in reptiles; taking the short 
diameter of the avian corpuscles as unity, the long diameter would 
usually vary between 13 and 2. But, as in Reptiles so in Birds, there 
are remarkable deviations from the regular proportions ; thus, e. g., 
in Columba migratoria (fig. 60), Lanius excubitor (fig. 56), and 
Syrnea nyctea (fig. 58) the length exceeds twice the breadth of the 
corpuscles, while in Columba rufina (fig. 59) and a few more pigeons, 
Dolichonyz oryzivorus (fig. 61), in species of Loxia and certain other 
Granivoree, the corpuscles have a much shorter oval figure. A mere 
glance at the Tables of Measurements will show how nearly the short 
diameters of the blood-disks of Birds agree with the diameters of the 
blood-disks in Apyrenzemata ; so that there is no bird in which such 
coincidence with some mammals is not obvious. 
Regularly the nucleus is more oblong than the entire corpuscle, so 
that the length of the nucleus is about twice, and occasionally nearly 
or quite thrice, its breadth. Hence this elongated shape exceeds 
that of the corresponding nucleus of other Pyrenzemata, and is cha- 
racteristic of Birds; but there are exceptions, as may be seen in some 
gallinaceous species, in which the nucleus is suboval or nearly glo- 
bular. 
Though in Birds the red corpuscles are regularly smaller than those 
of Reptiles, a few exceptions occur ; for example, the corpuscles are 
quite as large in the Cassowaries as in certain Saurians. And while 
Proc. Zoou. Soc.—1875, No. XXXI. 31 
