EGG-LAYING HABITS OF AMPHITRITE ORNATA VI.KKILL. 333 



quarter of the moon between June 29 and July 28." "All eggs 

 mature simultaneously at the time of the normal swarm." Later 

 observations ('09) show that the time of swarming is not so 

 definite as at first supposed. " When the last quarter of the 

 moon falls late in July there may be a response to the first 

 quarter as well as to the last quarter." " A dense swarm 

 occurred on July 10, 1908, a fairly dense swarm on July 19." 

 This behavior shows that a particular change of the moon has 

 no direct effect on the time of swarming, as the moon was in first 

 quarter July 6 and in last quarter July 20. Mayer also per- 

 formed an important experiment to test the effect of tides on the 

 time of swarming. He writes as follows : " Some worms swarmed 

 normally on July 19 out of the rocks which had been maintained 

 in a floating (tideless) live car for the six weeks previous to the 

 swarm." This experiment appears to demonstrate that tides are 

 without direct effect in producing the swarm. But, as Mayer 

 concludes, it "may indicate that the changing pressure due to 

 rise and fall of tide over the reefs is a contributory but not a nec- 

 essary component of the stimulus which calls forth the breeding 

 swarm." 



However, it is known that the tide may form a sort of habit in 

 the action of some animals. Gamble and Keeble ('06) have de- 

 scribed a small, green, sedentary turbellarian, Couvoluta roscof- 

 fcnsis, that occurs on the coast of Brittany. "It exhibits a peri- 

 odic vertical movement whose rhythm is that of the tide." 

 When the tide is out, they come to the surface, forming green 

 patches on the sand. When the tide comes in they retreat 

 below the surface into safer quarters. The remarkable fact is 

 that when removed from the effects of tidal action by being kept 

 in an aquarium, Convolnta continues to perform rhythmic move- 

 ments in time with the tide. "The rhythm is not profoundly 

 impressed upon it ; after a day the movements of the patch in 

 the vessel cease to synchronize with those in the open." This 

 illustration suffices to show how an action may arise in relation 

 to the tide without depending directly upon it. 



In Ampliitrite it has been observed that feeding is more con- 

 tinuous and more active as the time of spring tide approaches. 

 At such times the great mass of tentacles radiate from one 



