30 OSBORN. [Vol. XVIII. 



connection persists even to the spermatid stage. In my Fig. 45 

 the cells are not distinctly separated centrally, but in other clusters, 

 as in Fig. 47, they are distinctly so at the spermatogone stage. In 

 such cases there is no nucleus in the central mass. 



The spermatic duct is exceedingly slender, and for a long time 

 escaped my observation. It is recognizable by the presence in its 

 distal end of two or more small concretionary bodies which appear 

 to be constantly present. The duct leaves the anterior side of the 

 spermary and runs forward, crosses the body and passes into the 

 spermatic vesicle, not at the end of the latter, but at its inner side 

 a little in advance of its termination (Figs. 3, 35). This is quite 

 unlike the facts as indicated in Poirier's figure of the African form, 

 where there is no distinction between seminal vesical and sperm 

 duct, a passage of the same dameter running, according to him, 

 from the cirrus to the spermary. In Aspidogaster the sperm duct 

 is smaller than the seminal vesicle, but it enters the end of 

 the latter and not its side. The concretionary structures referred 

 to are not found in the spermary or in any other part of the 

 sexual apparatus. They are large and distinct, and consist of a 

 dark stainable interior surrounded by an outer translucent non- 

 stainable portion. One of them from a section is shown in Fig. 36. 

 I have not been able to account for them, and do not find mention 

 of anything similar in other trematodes. The seminal vesicle is 

 very variable in diameter and length in dififerent cases. In all cases 

 that I have seen it is either empty or contains a fine-grained 

 material in which no structures could be recognized. In no case 

 could I recognize any spermatozoa in it. Its .wall is composed of 

 nucleated cells, and muscle fibers are recognizable in it. It enters 

 the cirrus sack posteriorly and on the right side. At this point and 

 around the cirrus sack in Aspidogaster there are prostatic glands, 

 but I have not distinguished such in Cotylaspis. The cirrus sack 

 is oval and measures 0.26 mm. by 0.17 mm. It has a muscular 

 wall enclosing somewhat loose cells having much the appearance 

 of parenchyma, surrounding the cirrus in the center (see Fig. 34). 

 The latter communicates anteriorly with a sheath by means of 

 which the cirrus is everted, and posteriorly with a continuation of 

 the seminal vesicle, which enters the sack posteriorly. The cirrus is 

 walled by a muscular coat in which strong and numerous fibers are 



