2O8 K. E. JUST. 



very dense suspension of India ink in sea-water; or total dark- 

 ness. The reaction, therefore, cannot be due to sight. It is 

 more likely due to some chemical emanation from the gravid 

 female only since the spent female is not attractive to the male 

 (Cf. F. R. Lillie on Nereis, '12, '13.) 



A male Platynereis will embrace at least four females. On 

 the evening of August 24, 1911, for instance, I put a male and 

 a female in a dish. They swam around for a time, then the male 

 wrapped himself about the female just back of the head, he let 

 go, uncoiled himself, his tail remaining in the female's mouth. 

 Immediately after release, he was placed with a second female; 

 a minute later he induced oviposition. After intervals of five 

 minutes he embraced a third and fourth female. In all cases the 

 worms shed eggs. The male placed in fresh sea-water with an 

 active female after an hour (n P.M., about two hours in the 

 laboratory after capture) failed to make a fifth clutch. Other 

 males embraced two females. During 1912 and 1913 these 

 observations were verified. 



If after this egg laying behavior, both animals be removed 

 from the dish or if the eggs be pipetted off as laid the eggs develop 

 and normal swimming larvae much like those of Nereis limbata 

 result. If at the moment of her release by the male the female 

 be put in a dish of clean fresh sea-water, eggs will stream out and 

 subsequently develop. 



In all these cases sperm are attached to the vitelline membrane 

 within a hull of jelly which has been secreted through the break- 

 down of the cortical protoplasm of the egg. As in Nereis this 

 jelly formation begins at the moment that the sperm touches 

 the membrane. In Platynereis it is easily demonstrated that 

 the inseminated eggs have this jelly when laid. Mechanical 

 pressure either by the male, experimentally, or otherwise, as has 

 been repeatedly demonstrated, will not induce oviposition. Mere 

 clutching however recurrent even by more than one male is not 

 sufficient stimulus for oviposition. The head of the worm may 

 be crushed eggs will not escape; if she be cut in two, a few eggs 

 escape. Only after thorough drying on filter paper or on sheer 

 dry linen will the eggs burst through the body wall. If the 

 female be finely minced in sea-water practically all the eggs may 



