16 JOHNS HOPKINS UNIVERSITY MORPHOLOGICAL MONOGRAPHS. 



here be remembered that the interradial ganglia were probably 

 removed at the removing of the margin.) 



Cutting the nerve in the eight adradii caused the pedalia to bend 

 inwards at right angles to their normal position but did not in the 

 least affect the coordination of the sides. When, however, the sides 

 were cut in the eight adradii to the base of the stomach, coordina- 

 tion for the main part ceased, and ecfch side pulsated in its own 

 rhythm. 



I have said that the principal centers of spontaneity reside in the 

 radial ganglia. Upon further thought this hardly seems warranted. 

 No doubt, among the principal motor centers must be placed the 

 ganglionic masses of the clubs, and the radial ganglia, together 

 with the homologous interradial ganglia, represent centers of equal 

 value. I speak of these two sets of ganglia as homologous, since 

 strictly speaking, they both belong to the margin, and the clubs at 

 whose bases they lie probably represent modified tentacles. Conant's 

 experiments leave us in the dark as to the function of these ganglia. 

 Next in order, it would seem, are the ganglion cells in the suspensoria, 

 as is suggested by the contractions of an isolated side with a portion 

 of a suspensorium attached. (See previous head.) While we have 

 seen that the frenula and the velarium can contract by them- 

 selves, yet, I find no evidence that these can impart their con- 

 tractions to any adjacent tissue. 



Conant's results on cutting the nerve eight times and then 

 continuing the cuts to the base of the stomach are quite the same as 

 Romanes and Eimer obtained upon Aurelia. Romanes, however, 

 concludes that in his Sarsia, Tiaropsis, etc., coordination was broken 

 when only short incisions were made in the margin. Charybdea 

 appears, then, to agree with Aurelia rather than with the Hydrome- 

 dusa?. Yet, since Romanes at first obtained similar results to those 

 of Charybdea on Sarsia, but on further experimenting concluded that 

 coordination had really been destroyed at the first cutting, we cannot 

 speak with certainty that coordination had not been destroyed in 

 Charybdea before the cuts had been continued to the base of the 

 stomach. I say not with certainty, because the injury to the bell 

 being slight, coordination may have been maintained on the principle 

 of a simultaneously (simultaneous for the octants) alternate exhaustion 

 and recovery of the contractile tissue on the principle of Romanes' 

 theory. 



