ON THE OVIPAEOUS SPECIES OP ONYCHOPHORA. 375 



membranous walls, tliougli whether the difference is simply 

 due to stretching by the contained eggs may be regarded 

 as an open question. At their hinder ends the oviducts 

 unite in a thick-walled, muscular, triangular sac (figs. 4, 

 9, 10, Tr. S.), whose posterior angle is continued into the 

 ovipositor. Over this sac the nerve-cords pass, enlarging 

 upon its dorsal surface to form a pair of especially large 

 ganglia. The ovipositor is a thick-walled muscular organ, 

 with an outer layer of more or less longitudinally and an 

 inner layer of more or less circularly or obliquely arranged 

 muscle-fibres. Eggs were found in the middle and last 

 portions of the oviducts, but much more abundantly in the 

 last. Their number, of course, varies ; thus in one specimen 

 there were three eggs in each oviduct ; in a second, six in one 

 and seven in the other ; in a third, eight in one and nine in 

 the other. 



In 0. viridimaculatus the structure of the female repro- 

 ductive organs (figs. 27, 31) is closely similar, but I have not 

 detected any differentiation corresponding to that between the 

 second and third parts of the oviduct in 0. oviparus, while 

 the short proximal division of the oviduct in front of the 

 receptaculum seminis is devoid of distinct protuberances, 

 though its wall is folded. The number of eggs produced in 

 this species appears to be smaller than in 0. oviparus, for 

 of the two freshly killed specimens dissected, one (fig. 31) 

 contained only a single egg in the right oviduct and none 

 in the left, while the second (fig. 27) contained only two in 

 the right and one in the left oviduct; the former specimen, 

 however, had two very large ovarian eggs, apparently almost 

 ready to enter the oviducts (fig. 31). 



d. Eggs and Development. 



The Question of Oviparity. — Notwithstanding the 

 scepticism of certain writers, who have apparently never 

 thoroughly investigated the species in question, I do not 

 think that any impartial observer could hesitate for long in 



