102 OLIGOCHAETA 



differentiated than in the Lumbriculidae. But among the Eudrilidae, for example in 

 Libyodrilus, it is of considerable length, and not unfrequently possesses a muscular 

 sheath. In Alvania it has even a caecum lying close to it and bound up within 

 the same sheath. The position of the oviduct or oviducal pore, as the case may 

 be, varies in different families. It is remarkable that in all Megadrili the oviducal 

 ducts open on to the exterior in the fourteenth segment. Rhinodrilus proboscideus 

 may be an exception, but the statement that the ovary lies in the seventeenth segment 

 requires confirmation. In Libyodrilus the oviducal pores appear to be on the fifteenth 

 segment, but a dissection of the worm shows that the septum dividing the fourteenth 

 and fifteenth segments lies behind the point of opening of the ducts. 



Considering the close agreement between the male and female gonads the 

 differences between their ducts are perhaps more striking than the resemblances. 

 There is the general agreement that both consist of ciliated tubes opening into the 

 coelom by a wide funnel, often hidden within sperm-sacs or egg-sacs 1 . In both cases 

 the ciliated tube consists of a single layer of cubical cells, which may be surrounded 

 by a muscular layer in addition to the peritoneal coating. The caecum of the oviduct 

 in Alvania may be compared to the caecum of the sperm-duct in Phreodrilus. In 

 Phreoryctes too, which appears to me to be undoubtedly an archaic type, the oviducts 

 and sperm-ducts (there are two pairs of each) not only correspond in number and 

 structure, but the last pair of sperm-ducts is shorter than the first pair and is 

 therefore intermediate in length between it and the oviducts. 



In the Microdrili, indeed, the sperm-ducts and the oviducts agree in never occupying 

 more than two segments, the funnel lies in one segment and the external pore is in the 

 following one or rather between the two, and there is a relation between the position 

 of one orifice and the other (see Table above, p. 85). 



In the Megadrili the oviducts invariably occupy only two segments, while the 

 sperm-ducts nearly as invariably 2 occupy more than two segments. There is, 

 moreover, no ascertainable relation between the position of their pores, as the one 

 varies, while the other remains fixedly constant. The coiling of the sperm-ducts 

 is not paralleled by the oviducts ; and the latter are never connected with glandular 

 structures like the spermiducal glands. An apparent exception to this last statement 

 is shown by Eudrilus, where the oviduct opens in common with the spermathecal sac 

 and a glandular diverticulum apparently belonging to the same. This connexion, 

 however, is probably hardly comparable to the connexion between sperm-ducts and 

 spermiducal glands, since it is so rare among the Eudrilids (where alone it is found). 



1 Most completely in Eudrilidae. 



8 One exception is probably Telragununis. 



