BREEDING HABITS OF PTATYNEREIS MEGALOPS. 2OQ 



be procured. But eggs got in this way do not develop after 

 insemination; they will not fertilize in sea-water. I have sec- 

 tions of uninseminated eggs killed after having remained upwards 

 of two hours in sea-water; the cortical layer and the germinal 

 vesicle are intact. (So Nereis.} 



Eggs removed from worms after clutching only have the ap- 

 pearance of eggs from unembraced females no sperm attached, 

 subsequently no trace of development. Sperm are not found on 

 the female's body (e. g., hypodermic impregnation: cf. Whitman, 

 Gardiner, etc.) or near the anus at the time of egg extrusion. 



It appears, therefore, that mechanical stimulus is not sufficient 

 to excite oviposition or sperm shedding. The eggs are not laid 

 during or after the embrace nor are sperm shed unless the male's 

 tail has been in the female's jaws. This, then, is a case of copula- 

 tion followed by internal insemination. And indeed, the very 

 elaborate and precise behavior indicates this. The sperm 

 swallowed by the female inseminate the eggs in the body cavity, 

 oviposition following immediately. 



In 1911 gravid females before and after copulation were killed 

 in Meves fluid but proved too refractory for cutting; in 1912, 

 special precautions were taken. The following fixatives were 

 used : Bouin, Gilson, 10 per cent, formalin, and Hennings mixture. 

 With these mixtures the yolk and oil of the eggs are dissolved 

 out, but the chitin of the jaws still makes the procuring of 

 good sections difficult. In 1912 I thought that I had solved the 

 difficulty when after experiments with various agents I procured 

 with KC1, and KCN in sea-water eversion of the pharynx. 

 But in 1913, these methods gave very indifferent results. Dis- 

 section of the jaws gave almost negative results. My best sec- 

 tions are those of July, 1912, killed in Gilson, Series A; those of 

 August, 1912, killed in formalin, Series B, and those of 1913 

 kept in formalin for five months. 



Sections of gravid females killed before courtship show no 

 sperm in the body cavity. Sections of gravid females just after 

 copulation show sperm among the antennae, in the mouth, in the 

 pharynx, and in the body cavity. The sperm may be traced, 

 therefore, entering the mouth, passing down the pharynx whence 

 they escape through lesions in the pharyngeal wall to the coelom. 



