176 THE ANATOMY OF IXVERTEBRATED ANIMALS. 



back to the testis, and which would appear to correspond 

 with the internal vas deferens of other Trematoda described 

 by Von Siebold. 1 This canal, however, presents no dilatation, 

 or internal vesicula seminalis. The oviduct next receives the 

 duct of the vitellarium, and then becoming much convoluted 

 (&), and rapidly widening, passes into the uterus (/), a wide 

 tube, which runs forward, disposed in many undulating curves 

 (Fig. 40, I), to terminate on the left side of the anterior part 

 of the body, close to the male organs. Posteriorly, the walls 

 of the uterus are thin ; but in its anterior, or vaginal, part 

 they become thick and muscular. The genital vestibule into 

 which the vagina opens is very small. 



The testis (m) is an oval body of the same size as the 

 ovarium, and situated just behind it. Minute water-vessels 

 ramify upon it, as upon the ovarium ; and it contains a gran- 

 ular and cellular mass, but no spermatozoa. The external 

 vas deferens (Figs. 40 and 42) is a delicate duct, which 

 passes forward and comes into contact with the ovarium, 

 without, however, so far as I could observe, communicating 

 with it or with the oviduct ; it then bends backward and up- 

 ward, passing between the anterior vitellarian masses into 

 the fore part of the body. Here it suddenly becomes about 

 twice as wide as before, and runs forward, as an undulating 

 thick tube, to the penis (Fig. 40, p), a short and conical body, 

 occupying the bottom of a large pyriform sac, which opens 

 in common with the uterus. The spermatozoa are linear. 



The development of the ova presents many very interest- 

 ing peculiarities (Fig. 43). Above the junction of the duct 

 of the vitellarium with the oviduct the contents of the latter 

 were pale and clear, and presented no formed particles beside 

 the primary ova which had just been detached from the ova- 

 rium (Fig. 43, C). Below the insertion of the vitellarian 

 duct, however, the oviduct was full of granules like those in 

 the vitellarium, mixed up with ova in a more advanced state. 

 In the smallest of these (Fig. 43, D), the shell of the ovum 

 had commenced, but was incomplete at one end. At the op- 

 posite extremity, it inclosed a mass of irregularly aggregated 

 vitelline granules, which covered almost one-half of a round 

 pale mass, not larger than one of the primary ova ; in which, 

 however, three nuclei (two of which w T ere very close together, 



1 The connection of this duct with the testis in the Trematoda has recently 

 been denied by Stieda (" Midler's Archiv," 1871). I had no doubt of its exist- 

 ence in Aspidogaster, but I have had no opportunity of reexamining this ani- 

 mal since the publication of Stieda' s paper. 



