PHYSIOLOGY OF SYNAPTULA HYDRIFORMIS 341 



in one case to 21 hours in five cases. This means that, unless 

 carmine has an accelerating effect, it takes about 21 hours for 

 the food to pass from the mouth to the anus. 



In freshly collected synaptulas one can always see faeces in 

 the intestine at a distance from its anterior end slightly less than 

 half the length of the intestine. The castings are cylindrical 

 masses about 3 mm. long and 0.5 mm. in diameter, and are yel- 

 lowish white. Often there are two or three attached end to end. 

 Since there are regular rhythmic movements in the whole in- 

 testine, there may be some mechanism which determines the 

 form of these castings similar to that of Stichopus (Crozier, '16a). 

 Clark ('98, p. 56) states that in specimens from Jamaica "the 

 food consists largely of vegetable matter, diatoms being present 

 in the stomach." Microscopic examination of the contents of the 

 intestine and the faeces of Bermuda specimens failed to show 

 the presence of diatoms, but the empty walls of a small filamen- 

 tous (red?) alga were abundant. The chromatophores of the 

 alga and all parts inside the cell walls had disappeared in the 

 course of digestion. This difference in food between specimens 

 from Jamaica and from Bermuda is probably due to the greater 

 abundance of diatoms in the West Indies. 



The intestine of Synaptula shows strongly marked peristaltic 

 waves, which travel from the anterior to the posterior end, a di- 

 rection opposite to that of the irregularly occurring waves of 

 the body-wall. Since the animal is in constant motion and the 

 integument in most cases is not sufficiently transparent, at- 

 tempts to time these waves in the normally active animal were 

 not successful, but the average rate of pulsation in the intestine 

 of a Synaptula which was held upon a glass slide by weights and 

 whose body-wall was slit so as to disclose the intestine was ten 

 waves in 19 seconds at 27C. The average rate of pulsation in 

 the intestine after its removal from the body was ten waves in 

 28 seconds at the same temperature. 



The excised intestines assume a constant rate of pulsation 

 within 5 minutes after operation. In two cases, when they were 

 allowed to remain undisturbed, they were found to be pulsating 



