BREEDING HABITS OF PLATYNEREIS MEGALOPS. 2OJ 



escape, not through gonopores or the like, but through lesions of 

 the body wall (cf. Scott.) Eggs escape from three or more 

 posterior segments, occasionally from anterior segments. If 

 escape by way of the posterior segments be experimentally 

 inhibited, or if the female be slightly disturbed, the eggs seem to 

 burst through the body wall at segments more anterior than 

 otherwise. Females killed at the moment of oviposition show 

 tears in the body wall. 



After oviposition and the whole process just described is 

 in general the event of ten seconds the female sinks to the 

 bottom of the dish, a mere shred. In the laboratory placed in a 

 little water it remains an irritable sticky mass for a time in- 

 capable of exciting fresh males and finally dies, greatly shrivelled 

 and blackened. Often, however, if flooded with fresh sea water 

 it revives, expands to previous size, and swims around actively, 

 almost perfectly transparent. I have kept these spent females 

 alive for several hours. Since there are no sexual segments as in 

 some annelids, but the whole body is little more than a locomotor 

 ovary, it seems safe to assume that this egg-laying marks the 

 end of the worm's existence. 



Both animals must be in healthy condition for this behavior. 

 Active males sometimes grasp females which because of rough 

 handling in capturing are doubtless weak and fail to respond. 

 The active males on the other hand are not very hardy: in the 

 laboratory they rarely live twenty-four hours; one experiment 

 made in 1913, failed to show any difference in the vitality of spent 

 and unspent males. Normal females when placed in dishes with 

 males fail to complete the courtship if the vitality of the male as 

 by rough handling be impaired. Males and females may be 

 kept in the same dish until death; if there be no courtship, 

 there is no oviposition. Female Platyneris and male Nereis 

 show no excitement when in the same dish, so male Platynereis 

 and female Nereis. The male Platynereis ordinarily will em- 

 brace only an unspent female Platynereis. But on one occasion 

 (July 23, 1913) all (8) males captured in turn and repeatedly 

 embraced a Nereis virens eight inches long whose posterior seg- 

 ments had been lost. Once only I saw a male clutch a female 

 which had extruded part of her eggs after a previous courtship. 



The animals will go through this courtship when placed in a 



