STUDIES OX THE ECTOPAEASITIC TREMATODES 01' JAPAN. IQo 



itself at the middle, so as to foi'ni a loop across the length of the 

 body ; but in this genus the proximal end of the ovaiy, /. e., the zone 

 of formation, is enlarged into a globular shape, while the remaining 

 portion is throughout of an almost uniform thickness so that AVierze- 

 jski'' was led to call this portion the oviduct (Eileiter). But that 

 it corresponds in reality to the zone of growth is very clear from 

 a comp.arative study of the ovary in different genera. What 

 seems to he very peculiar is that the closed end of the loop which 

 the ovary forms in this genus encircles the intestine (PI. XIX, 

 fig. 1). This is also the case in Manocotijle ; but in this genus the 

 formative zone passes gradually into the zone of growth, and the whole 

 ovary makes an additional large winding or two (PL XVII, fig. 1). 



In Dicliclophora tlie form of the ovai-y varies much in different 

 species. The simplest form is found in Dlclid. clongata, in which a 

 long cylindrical ovary is twice bent on itself so that each half is horse- 

 shoe shaped (PI. X, fig. 9). In Didid. sessilis also, each half of the ovary 

 is bent on itself so "that the whole looks somewhat like the letter W; 

 but the four arms of the W are closely applied to each other, and the 

 terminal portion, /. c, that which gives rise to the oviduct is very 

 much larsrer than the other three, and contains a cavitv filled with 

 a sparsely fibrous connective tissue (PI. X, fig. 5). In Diclid. 

 tetrodonis, again, the somewhat comma-shaped ovary makes a spiral 

 windins: to one side at its middle, so that the whole looks some- 

 what like the embryo of the chick in profile, with its large heart 

 protruding from its ventral side at a short distance from the head 

 (PI. X, fig. 1) ; the head of the embryo answering to the oviduct 

 end of the ovary .and the tail end to the formative zone. In Onclwco- 

 tijle the zone of formation occupies about one-fifth of the Avhole length 



1). Wierzejski— Znr Kenntniss des Baues von Calicotyle Kroyeri. Zeitsclir. f. wiss. 

 Zoolog., Bd. 29, 1877. p. 557. 



