122 The American Naturalist. [February. 
part due to physiological reasons, yet it is in so far a zoological 
one as the whole “ physiognomy ” of the dorsal segment of the 
cord in the Cetacea is more like that of the Ungulata than the 
Carnivora. A section of the spinal cord at the level of the 
foramen magnum has, in every genus, something distinctive, in 
every family something quantitatively different from other fam- 
ilies, in every order something qualitatively and radically distin- 
guishing it from nearly related orders. While, as already stated, 
such differences have not the profound morphological meaning 
which certain cerebral features possess, yet it is not from attach- 
ing any over-importance to the field to which I have devoted 
most of my dilettante studies that I venture to prophesy that 
when the minute and coarse anatomy of the nerve axis be once 
thoroughly known for each species it will be possible to offer a 
more correct classification of the Mammalia than any now ex- 
tant, or any other based on a single criterion. It would not be 
difficult to enunciate many valuable data for classification furnished 
by a study of the nerve centres in Sauropsida and Ichthyopsida. 
Many peculiarities of the appendages of the brain among the 
former, such as the cartilaginous epencephalic hood of the 
Chelydra, and the cartilaginous rod attaching the oblongata to the 
basi-occipital bone in Thalassochelys, require and will repay 
further study. It is in view of the importance of registering 
only correct observations that I offer this provisional correction 
of such revolutionary pseudo-discoveries as those above criticised. 


