1885.] Recent Literature. L197 
tion as do the entire animals. They also crawl up perpendicular 
surfaces, and sometimes away from injuries, though not generally 
seeking to escape the latter as do the entire animals. By sever- 
ing the nerves at the base of each of the five rays, or by dividing 
the nerve-ring between all the rays, the animal loses all power of 
coordination among its rays (Figs. 14, 15). If a continuous cir- 
cular section of the external surface of the sea-urchin was made, 
it was invariably found that the spines and pedicellariaz within 
Fic. 12.—External nerve-plexus of Echinus. 
the circular area immediately respond to stimulation, while none 
outside the circle are affected. “ These facts prove that the func- 
tion which is manifested by these appendages of localizing and 
gathering round a seat of stimulation, is exclusively dependent 
upon the external nerve-plexus.” From these and other experi- 
ments, and the histological studies of Professor Ewarts, it is con- 
cluded that the nervous system of an Echinus consists (1) of an 
