NOTES ON SOME PROBLEMS OF ADAPTATION. 



3. THE VOLUME OF WATER INVOLVED IN THE CLOACAL PUMPING 

 OF HOLOTHURIANS (STICHOPUS) - 1 



W. J. CROZIER, 

 HULL ZOOLOGICAL LABORATORY, UNIVERSITY OF CHICAGO. 



It has been of interest, especially in connection with studies of 

 respiration, to determine the volumes of seawater which various 

 marine animals pass through their respiratory organs. With the 

 sponge Spinosella Parker ('14) calculated from his measure- 

 ments that something like 78 liters a day was the volume forced 

 through a single " finger " of the body of this sponge. For As- 

 tidia, Hecht ('16) showed that the branchial stream was prob- 

 ably somewhat in excess of 173 liters per day, in individuals of 

 medium size. The water current in such cases (the only ones of 

 the kind carefully investigated) brings not only oxygen but food 

 particles as well, and in addition has an excretory significance. 



I undertook to measure the volume of seawater involved in the 

 cloacal pumping of a holothurian such as Stochopus wux'bii, in 

 which water is forced into respiratory trees and then expelled to 

 the exterior. The cloacal chamber of Stichopus pulsates with a 

 frequency which depends on the size of the animal ; after a cer- 

 tain number of pulsations the water contained in the respiratory 

 trees is forced out ; the number of pulsations between two acts of 

 "spouting" also depends on the size of the individual (cf. Cro- 

 zier, '16). As in all such cases, the expelled water is forced out 

 rather violently, driven to a considerable distance, so that it is not 

 readily taken in again when inspiration is again begun (Hecht, 

 '16; Arey and Crozier, '19). 



By previously ascertaining the mean number of inspiratory pul- 

 sations elapsing between " spoutings," it was possible to remove 

 a given Stochopus from the water just before the beginning of 

 an expiratory act, and to receive the discharged water in a funnel 



i Contributions from the Bermuda Biological Station for Research. No. 122. 



130 



