SPINAL CORD. IO 



brates. It contains no large cells in its inferior horns. An apparent 

 exception is to be noticed in Plate XX. in, box turtle large cells be- 

 ing shown in a section which was made just in front of the lumbar en- 

 largement. Sections of the middle dorsal region, from the same speci- 

 men, were found to be free from large cells. 



Thickness of the Spinal Cord, in its Anterior 

 and Posterior Regions, Compared. 



Alligator. Tail powerful. Posterior equals Anterior. 



Iguana. " " " exceeds* " 



Phrynosoma. " rudimentary. Anterior " Posterior. 



Anolius. Tail long but weak and fragile. " " " 



Skink. " large " " " " " " 



Heloderma. " " " " " " " 



Turtle. Tail rudimentary. " much exceeds " 



Chelydra.f " well developed. " exceeds " 



Tailed Batrachians. " " " " equals " 



Tailless " " much exceeds " 



Plate XVIII. gopher turtle represents the inferior horn of one 

 side from a cross section through the middle of the cervical enlargement. 

 The group of large cells, multipolar and bipolar, in which the nuclei 



* This apparent anomaly loses its force, as such, when one considers that the 

 difference in thickness, between the enlargements, is small, and depends upon an 

 increase of gray substance, corresponding with a difference in development between 

 the two pairs of extremities greater than in the alligator. 



t In the snapping turtle, the tail, although it is powerful, occupies in respect to 

 its development, a position intermediate between that of the common land turtle and 

 the alligator, thus corresponding with the lumbar enlargement which is relatively 

 thicker than in the ordinary turtle. Compare Plates XXII. & XXIII. with XIX. I, in. 



