524 A. MILNES MARSHALL. 



contact with a piece of stick, it attached itself to it by the 

 dorsal cirri, and remained there for more than a Aveek. 



The above experiment is the same as Dr. Carpenter^s 

 Experiment B described above. It is extremely important as 

 proving that the co-ordinating mechanism which regulates the 

 complex swimming movements of the arms is entirely without 

 the visceral mass. As the direct connection between the sub- 

 epithelial bands of the several arms is also destroyed, the 

 experiment renders it extremely doubtful whether these bands 

 have any part in regulating the swimming movements of the 

 arms. 



Experiment 2. — An active specimen was eviscerated, and 

 allowed to come to rest. The ventral surface of one of the 

 arms was then irritated gently with a needle ; active move- 

 ments both of the irritated arm and of the others resulted. 

 The same effect followed irritation of one of the ordinary 

 pinnules ; while irritation of the oral pinnules caused immediate 

 and strong flexion of all the arms. 



This shows that the eflfect of irritation of the arras or 

 pinnules is practically unmodified by the removal of the vis- 

 ceral mass ; the only difference I have noted being that the 

 response is slightly quicker and more extensive in an evis- 

 cerated than in an uninjured specimen. The nervous con- 

 nection between the sensory epithelium of any one of the arms 

 or pinnules and the muscular system, not only of that arm, 

 but of all the others as well, must, therefore, be without the 

 visceral mass. 



As a source of irritation in this and other experiments I 

 employed at first scratching with a sharp needle. I found 

 afterwards that nipping with forceps was preferable, as the 

 needle is apt to shake the whole animal, and so cause dis- 

 turbance of parts other than those it is desired to irritate. 

 The nip should be a sharp sudden one, and the irritated part 

 released at once. In all the experiments here recorded, except 



