SPAWNING HABITS OF CUMINGIA TELLINOIDES. 429 



time of spawning, so that any change from this time could be 

 regarded as an experimental modification. 



SUMMARY. 



1. The spawning season of Cumingia extends from the middle 

 of June until the middle or end of September. The most active 

 spawning usually includes the last week in June and ends about 

 August 20. Each female spawns more than once and the 

 production of gametes is practically continuous. 



2. The spawning is heaviest from full moon to new moon and 

 least at first quarter thus showing a lunar periodicity. 



3. Cumingia is greatly affected by shock and rough treatment 

 so that sexually mature individuals spawn promptly when 

 brought to the laboratory, after being placed in a bowl of quiet 

 sea water. 



4. There are apparently no chemical stimuli by which the 

 sexes stimulate each other to sexual activity as is the case in 

 Nereis limbata and the oyster. They spawn as readily when 

 isolated as when in close proximity. 



5. It is shown that temperature is not the only factor which 

 determines the duration of the spawning season and periods of 

 spawning. 



SPAWNING EXPERIMENTS. 1922. 

 CUMINGIA TELLINOIDES. 



Table No. I. 



Cumingia spawned vigorously during the first half of August but stopped 

 suddenly about August 15. Several investigators were experimenting upon 

 Cumingia eggs at that time and noted this fact. All collections were made at 

 low tide or within an hour of low tide at the convenience of the supply department 

 of the laboratory. 



* September 21, new moon. 



I. 8/23. No eggs spawned, i male shed sperm abundantly. 17 did not 



spawn. 

 II. 8/24. No eggs and no sperm. 



III. 8/27. No eggs spawned. 4 males shed sperm small amount. 14 did not 



spawn. 



* September 28, first quarter. 



IV. 9/1. 5 females spawned in quantity. 6 males shed sperm, 3 in quantity, 



3 in small amount. 7 did not spawn. 



Comment. This revival of spawning after the spawning season had apparently 

 ended is surprising. The quantity of eggs shed is equal to mid-season spawning. 





