RHYTHMIC PULSATION 



323 



That the integumentary part of the apparatus does normally 

 enter into transmission is indicated by tests made under the 

 following conditions: 1) with the skin completely cut through 

 on one side (fig. 19), and 2) with cloacal sphincter cut into lateral 

 halves (fig. 20). 



In the first case the sphincter and cloaca on the cut side lagged 

 behind the opposite side, both in systole and in diastole. 



Figs. 19, 20, 21 For explanation see text 



In the second instance the brim no longer pulsated in coordi- 

 nated manner and ceased to move after a few minutes. If one 

 of the halves was gently pinched, it reacted alone, by the con- 

 striction of its circular muscles; whereas if stimulated more 

 vigorously, or if a nearby point on the skin was stimulated, both 

 halves of the brim contracted, the one nearer to the irritated 

 place contracting sooner. 



The effects of stimulation are thus conducted in a radiating 

 fashion, such as would result if an ectodermal nerve-net were 

 operating, and I conclude that such a net is present. 



