THEORY OF NERVE COMPONENTS. 



II 



One of the best illustrations of this central response to 

 peripheral differentiation is found in the sea-robins, in 

 which certain free rays of the pectoral fins have become 

 exceedingly sensitive finger-like tactile organs and their 

 sensory nerves, together with the corresponding dorsal 

 horns of the spinal cord, have been in consequence enor- 

 mously hypertrophied. 



This brain is strictly typical for the bony fishes, but the 

 proximal end of the spinal cord exhibits a series of re- 

 markable lobes which are the terminal centres for the 



Text-Figure 2. 



Text-Figure 2. — Brain of Carpiodes as seen from above. After 

 C. L. Herrick. Lob. vag. — lobi vagi; other letters as in fig. i. 



sensory nerves from the free rays. (Text-figure i). Here 

 the exaggeration of the general cutaneous component of 

 these first three spinal nerves evokes a perfectly definite 

 and easily recognizable response in the central system. 



