HEAT PRODUCTION BY EGGS. 



341 



of very careful evacuation. The flasks were submerged in 

 running sea water to within a short distance of their tops, and a 

 water cap (d) made according to a design by White (9) was 



FIG. i. Diagram of experimental set-up. I. and II., Vacuum flasks, a, 

 main thermopile, b, auxiliary thermopile, c, c, stirring tubes, d, water cap. 

 e, sperm pipette. 



placed over them. A pipette (e) projected through the cap and 

 was arranged so that "dry sperm" could be held in it, and then 

 mixed with the contents of flask (I.) whenever desired. A 

 continuous flow of water was maintained through this cap so 

 that the whole formed a uniform temperature enclosure. The 

 sea water temperature remained fairly constant except for periods 

 of about four hours after sunrise and sunset. The variation of 

 temperature never exceeded 0.001 C. during the period occupied 

 by an experiment. 



STIRRING APPARATUS. 



It has been noted by many investigators that eggs of Echino- 

 derms must not be heaped upon each other if normal development 

 is to take place. In our work it was desirable to use as large a 

 number of eggs as possible in order to get the largest possible 

 temperature change. It was therefore necessary to devise some 

 method of stirring the eggs which would render it impossible 

 for them to settle to the bottom of the flask and remain there for 



