BOTTOM MATERIAL INGESTED — ^HOLOTHURIANS 



385 



also move into deeper water at nightfall, and gradually creep 

 up to near the surface during the morning hours. 



I quote from a record of observations made during a single day ; 

 these records are typical of my findings upon other occasions. 



Rocky spit near Fairy- 

 land Creek 



8 :00 A.M. No castings 

 visible 



10:30-11:00. Of G3 ani- 

 mals, 60 in the pro- 

 cess of defecating. 



4:30 p.m. Of 48 animals, 

 all had castings near 

 them or were de- 

 fecating. 



Bay north of Saltus 

 Island 



S : 30 A.M. No castings 

 apparent; 5 animals 

 opened had the in- 

 testine well filled. 



10:00. Castings plenti- 

 ful ; of 6 opened, only 

 1 animal had sand in 

 the gut. 



2:00 P.M. No castings; 

 11 opened; all were 

 full or at least (2 

 cases) f full. 



4:45. Of 28 animals, all 

 exhibited castings. 



December 12, 1917 



Agar's Island 



7 : 05 A.M. No castings 



visible 

 7:30-8:00. Castings by 



10 of the 12 inspected 



animals. 

 9:30. 10 full, 1 filling, 1 



emptying, 1 emptj- 



(13 opened). 

 11:00. Of 8 animals, 4 



had begun castings. 

 11:30. 8 dissected; 5 



empty, 2 well filled, 1 



with oesophagus and 



stomach full. 

 4:30 P.M. No castings 



visible; 4 examined 



had the intestine 



well filled. 



It follows that these holothurians were probably engaged in 

 filling the intestine at least three times in the twenty-four hours. 

 During daylight, the process of filling and emptying appears to 

 occupy, at a temperature of about 20°C., a period of about 5-0 

 hours. In utilizing these results for further calculations, I have 

 considered that in any given littoral situation frequented by 

 Stichopus each animal fills the gut twice each day. It seems 

 reasonable to make this restriction owing, 1) to the fact that at 

 night the holothurians retreat into deeper water, and 2) to the 

 fact that in stormy weather they remain well below the water 

 Surface, except in protected places ; this restriction is probably of 

 a character to diminish, rather than to enhance, the calculated 

 tilling of the sea-bottom by Stichopus. The observations on 

 feeding showed that animals of all sizes between 10 and 80 cm. 

 length fill the intestine with about the same frequency. 



