1875. ] RED BLOOD-CORPUSCLES. 479 
except in the Lampreys; largest in the tailed Batrachians and Lepi- 
dosiren; and then follow, in the order of the size of the corpuscles, 
Rays and Sharks, Frogs and Toads, Reptiles, Birds, and osseous 
Fishes, with certain exceptions, which may be seen in the Tables of 
Measurements. Among the oval corpuscles, whether in Pyrenzemata 
or Apyrenzemata, a few may deviate by gradations to the circular 
shape. Of these terms Pyreneemata and Apyrenzemata, here applied 
to the two great sections of the Vertebrate subkingdom, an account is 
given in my Lectures cited above, also in the second volume of the 
‘ Journal of Anatomy and Physiology,’ in the ‘ Proceedings of the Zoo- 
logical Society,’ Feb. 25, 1862, and in the ‘ Hunterian Oration,’ 1863. 
FIsHEs. 
In no other vertebrate class are the red blood-corpuscles so diffi- 
cult to measure as in this, wherein they are prone to rapid septic con- 
ditions, are singularly delicate in outline and substance, and hence 
most liable to changes of shape ; in all of which points the corpuscles 
of Fishes contrast remarkably with those of Reptiles and Birds. 
Form of the corpuscles.—Throughout the Vertebrates this is a disk, 
like a cake or coin; and hence the term blood-disk ; but it is never so 
thin proportionally as a coin, and in fishes the thickness is about one 
third of its short diameter. The corpuscles are circular in the Lam- 
preys, as figured with details in the ‘ Proceedings of the Zoclogical 
Society,’ Dec. 6, 1870, p. 845; but in all other fishes more or less 
oval, so far as we yet know. If we consider the short diameter of 
_ the corpuscle as 1, the long diameter will usually be between 14 and 
12; and the nucleus has much the same figure, and is often nearly 
or quite globular. But these proportions are variable, since the 
corpuscles are frequently suboval ; and in such cases several of them 
assume, by gradations, a circular shape, while those of the suboval 
form predominate. This may be plainly seen, for example, in the 
Anacanthini, especially a few hours after the death of the fish ; and 
then, in other orders besides that, the corpuscles are apt to present 
angular, fusiform, lanceolate, erescentic, oat-shaped, and still more 
irregular forms, all of which commonly exist in the blood of Gadidze 
and Clupeidze obtained from fishmongers. In some Acanthopteri 
and Malacopteri, as Scomber, Caranz, Lophius, and Salmo, and the 
great Eels of Rodriguez, good examples occur of well-defined oval 
corpuscles. In the Pike most of them are somewhat pointed at the 
ends. In the osseous fishes there is generally, but not always, a 
rounded projection on each broad surface of the corpuscle, caused by 
the nucleus and a groove between it and the margin of the disk. 
And in no Pyrenzemata has the regular red corpuscle that concavity, 
gradually deepening towards the centre (Plate LV. fig. 2), which is 
characteristic of the regular corpuscle in Apyreneemata, and has often 
been mistaken for a nucleus. 
Size of the corpuscles.—In the osseous fishes the largest corpuscles 
are those of the Salmonidze, as figured in the ‘ Proceedings of the 
Zoological Society,’ Nov. 19, 1872, p. 835; but though this large- 
ness is plain in Salmo, Trutta, and Thymallus, it disappears in 
