102 Proceedings of the Royal Physical Society. 



Testes and Sperm sacs. 



The statements of previous writers about the male gonads 

 and the sj^erm sacs are a little contradictory. 



Claparede remarked (1) that in Pachydrilus verru- 

 cosus "the testis is not single, as in the preceding species 

 {P. semifuscus, P. crassns). There are generally at least 

 eight pear-shaped testicles. They fill the ninth and tenth 

 segments, their pedicles converging towards the same point 

 on the wall of the ninth segment, where they are inserted in 

 common. They form then a kind of bouquet." 



Vejdovsky (3, p. 39) writes that in P. 2^agenstecheri " there 

 are a number (6-8) of pear-shaped bodies attached to the 

 anterior side of the septum separating segments 10 and 11, 

 which when fully developed completely fill the 10th and 

 11th segments. They are attached to the septum, and not 

 to the body-wall, as Claparede states. The youngest stages 

 of the testes in Pachydrilus form small clear sacs out of the 

 inner epithelium of which the seminal cells arise. The 

 outer wall of these organs consists of polygonal cells, with 

 an obvious nucleus and nucleolus (pi. xiv., fig. 9, ep) ; 

 under this is a feeble musculature and the inner epithelium 

 producing the spermatozoa. . . . Eipe spermatozoa 

 are set free into the body cavity by dehiscence of the 

 testicular walls." Vejdovsky, in a later work (4, p. 135), 

 considers that the organs which were regarded by himself 

 (in 3) and by Claparede as testes are" really sperm sacs ; 

 according to this view, the testes of Pachydrilus have yet to 

 be found. 



Dr W. Michaelsen of Hamburg, who has lately taken up 

 the study of the EnchytrseidaB, and has published a number of 

 valuable papers upon their anatomy, has found himself unable 

 to agree with the later views of Vejdovsky just referred to. 



Michaelsen considers (2, p. 62) that the organs in question 

 are after all testes, at any rate in the genus Pachydrilus. 

 Sperm sacs are, according to Michaelsen, only found among 

 the Enchytrseidse in Mesenchytrceus. 



I have found the testes to be larnjest in individuals oiot 

 sexually mature, where they form a bunch of divergent 



