PHYSIOLOGY OF SYNAPTULA HYDRIFORMIS 373 



indicated by the fact that the concentration of KC1 which just 

 failed to stimulate Synaptula was 1/50 M, while for KBr it 

 was 1/80 M. Therefore we find this series to be: chloride, 

 bromide, iodide (Hober, '11, p. 487). 



No attempt was made to carry out experiments on 'balanced' 

 solutions, since calcium-free sea-water proved stimulating. In 

 60 trials with calcium-free sea-water, conducted at different 

 times during the summer on many different specimens of Synap- 

 tula, 31 resulted in vigorous responses, 11 in slight responses, 

 and 18 in no response. There was no reaction to magnesium- 

 free sea-water. The effect of calcium-free sea water is plainly 

 shown in the following record. The individuals were gently 

 transferred from ordinary sea-water and totally immersed in 

 the calcium-free sea-water. Similar transference from normal 

 sea-water to normal sea-water, carried out as a check, caused 

 no reaction. 



July 26 



4.15 p.m. Five individuals transferred to calcium-free sea-water. All five at 



once contract body, then draw in tentacles violently, then straighten 

 out. 



4.16 p.m. Violent peristaltic waves of body wall in quick succession. No at- 



tempts to climb the sides of the dish. Squirm about on bottom. 

 Three individuls defecate. 



All much contracted, lying motionless on bottom. 



Do not respond to slight touch, or even vigorous poking, or to solu- 

 tion of 1/400 M HC.l 



Restored to normal sea-water. 



Four perfectly recovered. Climb walls. Respond to touch, etc. 

 Others still motionless. 



July 27 

 All five animals in perfect condition. Respond to touch, etc. 

 Calcium-free sea-water therefore acts as an anaesthetic. 



Local application of solutions of chemical agents to different 

 parts of the body gave characteristic results. Fifteen trials 

 where 0.5 cc. 1/10 M KC1 was allowed to flow very gently from 

 a capillary pipette ending about 2 mm. from the regions to be 

 stimulated gave the following: 



1. On tentacles. Tentacles close and animal drops. 



2. On mid-body. Local contraction, which initiates a peristaltic wave. 



3. On posterior end. Local contraction. Posterior end lashes about from 

 side to side. In one case the animal contracted its tentacles and dropped. 



