246 B. H. GRAVE. 



EXPERIMENTS, 1921. 

 Experiments on Chcstopleura. Summer of 1921. 



* Full moon, June 20. 



I. 



Experiment i, June 24-26. 



ist night, of twenty-five large chitons collected June 24, three and 

 possibly four spawned in fair quantity, first night, perhaps 

 50-60 per cent, of maximum; none spawned before 10 P.M. 



2d night, spawning began at 10.30 P.M.; probably over before 

 midnight, as indicated by development of embryos next morn- 

 ing; five females out of twenty-five animals spawned one half 

 to two thirds maximum; good quantity. 



Remark. Experience of last year has shown that most of the 

 spawning is done the second night after collecting. Therefore, it 

 is best to consider only 2d night in studying spawning habits, or 

 else compare experiments as a whole. 



* Last Quarter, June 28. 



II. 



Experiment 2, June ^o-July 2. 



30 specimens collected June 30. 



ist night, no females spawned; a few males shed sperma- 

 tozoa (2 or 3). 



2d night, three females spawned about one half maxi- 

 mum. 



3d night, two females spawned in considerable quantity, 

 a third one lightly. 



Remark. Impression of good spawning activity during the last 

 week in June. Plenty of eggs for embryological study. Isolated 

 specimens also spawned readily and in quantity. 



III. 



Experiment 3, July 2-5. 



60 specimens collected Saturday, July 2 ; 30 placed in running 

 water and 30 placed, as usual, on laboratory tables. 



