SPAWNING HABITS OF CH.ETOPLEURA APICULATA. 24! 



sexual products, and that it may also be the immediate cause of 

 swarming. 



A theory proposed by Brunelli and Schroener, 1 that the swarm- 

 ing has its origin in original accidental shocks to the nervous sys- 

 tem of these worms, and that their swarming activities finally be- 

 came spontaneous or hereditary in a form that was favorable to 

 the propagation of the species, is probably true, but it explains 

 nothing. That the habit of spawning periodically has become 

 hereditary is shown by the fact that the animals under discussion 

 will spawn at the proper time even when the normal stimuli are 

 altered or absent. See Mayer ('07). 



Most of these theories are based upon abstract reasoning and 

 not upon experimental data. It is apparent that there is something 

 yet to be done before we can understand this curious phenomenon 

 and its relation to the moon. That this habit has become more or 

 less hereditary is shown by several authors. However, it must 

 have originated in relation to external stimuli which are felt peri- 

 odically. The cause of this type of periodicity must be funda- 

 mentally the same in all cases, although it is exhibited in a variety 

 of ways, and at different times relative to the phases of the moon. 



EXPERIMENTS ON CH^TOPLEURA. 

 Summer, 1920. 



I. 



June 2023 : 



20 Chitons collected June 20. 

 ist night, no eggs. 

 2d night, no eggs. 

 3d night, no eggs. 

 * First Quarter, June 23. 



II. 

 June 24-27 : 



30 Chitons collected June 24. 



ist night, no eggs, some spermatozoa. 

 2d night, no eggs. 

 3d night, no eggs. 



* It is due to the last two authors mentioned to state that the writer has 

 read only quotations from their papers. 



