296 JELLY-FISH, STAR-FISH, AND SEA-URCHINS. 



The only other experiments in nerve-section to 

 which the simple anatomy of a Star- fish exposes 

 itself is that of dividing the nerve-ring in the disc; 

 or, which is virtually the same thing, while leaving 

 this intact, dividing all the nerves where the}^ pass 

 from it into the rays. In specimens mutilated by 

 severino: 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 co-ordination 

 among its rays. When a common Star-fish is so 

 mutilated it does not crawl in the same determinate 

 manner as an unmutilated animal, but, if it moves 

 at all, it moves slowly and in various directions. 

 When inverted, the power of effecting the righting 

 manoeuvre is seen to be gravely impaired, although 

 eventually success is ahvays achieved. There is a 

 marked tendency, as compared with unmutilated 

 specimens, to a promiscuous distribution of spirals 

 and doublings, so that instead of a definite plan of 

 the manoeuvre beino^ formed from the first, as is 

 usually the case with unmutilated specimens, such 

 a plan is never formed at all ; among the five rays 

 there is a continual change of un-coordinated move- 

 ments, so that the righting seems to be eventually 

 effected by a mere accidental prepotency of some of 

 the righting movements over others. Appended is 

 a sketch of such un-coordinated movement, taken 

 from a specimen which for more than an hour had 

 been twisting its rays in various directions (Fig. 57). 

 Another sketch is appended to show a form of 

 bending which specimens mutilated as described 

 are very apt to manifest, especially just after the 



