INTEENAL ANATOMY. 83 



and Gudden's figure of those of T. siro is similar ; 

 but Nalepa figures those of Garpoglyphus anonymus 

 as being more elliptical, the ellipse having its long 

 axis transversely across the body, the vas deferens in 

 the centre of the anterior side, and the spermatogenous 

 layer chiefly on the posterior side. The testes have a 

 soft tunica propria, but not any muscular or epithelial 

 layer. 



Nalepa gives the following account of the develop- 

 ment of the sperm elements in T. longior. The central 

 part of the testis is a finely granular protoplasmic 

 mass in which numerous long nuclei are imbedded ; 

 near the centre they are crowded and small ; near the 

 periphery less numerous and larger. These nuclei are 

 the starting-point for the formation of spermatoblasts ; 

 they grow greatly, become roundish ; while the proto- 

 plasm surrounding them separates itself from the 

 adjacent plasma; finally they become formed cells, 

 united by protoplasmic threads. The spermatoblasts 

 scarcely increase in size ; they have a diameter of about 

 0036 mm. They are difficult to stain with ammonia- 

 carmine ; the nuclei are round and uni-nucleolar. 

 Their number causes an expansion of the wall of the 

 testis ; through mutual pressure they lose their round 

 form and become hexagonal, so that the testis looks as 

 if covered with pavement epithelium. In each portion 

 of the testis near the vas deferens the zoosperm is 

 developed by unknown division of the spermatoblasts. 

 They are round, large-nucleated cells, with a diameter 

 of scarcely '0036 mm. They colour deeply with car- 

 mine. In the vas deferens they become long-shaped 

 from pressure. 



The Vasa Deferentia. In Qlycyphagus plcdygaster a 

 long, flexible vas deferens (PL B, fig. 2, v d) starts from 

 the smaller, anterior end of each testis ; and continues 

 separate from its fellow of the opposite side of the body 

 until near the penis : it is much the widest where it 

 leaves the testis, and is not sharply differentiated from 

 that organ, which fades gradually into it ; the diameter 



