220 HENRY LESLIE OSBORN 



have just considered [C. marginatum] that I have not the least 

 hesitation in concluding that the}^ are the same." The form of 

 the uterine sack however is very different in D. reticulum from that 

 of C. marginatum or of any other member of the genus. Accord- 

 ing to fig. 26 of Looss' article ('85) the sack is extended posteriorly 

 dorsally to the testes until it reaches a point posterior to the pos- 

 terior testis. This posterior development of the sack is a feature 

 not found in any of the species of this genus so far as I am aware. 

 In the several species included by Braun ('00) in his article on the 

 group, the sack ends in advance of the genital pore. If Looss was 

 not in error in regard to the form of the sack (and this seems very 

 improbable) then we must recognize that D. reticulatum differs 

 decidedly in this respect from the rest of the genus. However 

 in any case we should not attach very much importance to differ- 

 ences in the shape of an organ like the uterus or its parts. 



Meiraterm. There is a short slender tube running from the 

 sack to the atrium (figs. 3 and 4 E) which, following the nomen- 

 clature suggested by Ward ('94), may be called the metraterm. 



Vitellaria. The vitellaria are shown in fig. 1. They are dif- 

 fusely scattered in all parts of the region behind the ventral sucker. 

 As shown by transverse sections they lie in a thin zone, concen- 

 tric with the surface and next to the outer wall of the body. They 

 are entirely absent from the anterior part of the body. The vitel- 

 laria are made up of ultimate follicles, all of them very small and 

 numerous measuring 0.07 mm. These are bounded by a distinct 

 membrane which encloses a few yolk cells which measure 0.0125 

 mm. in diameter. Usually the vitellaria cannot be seen in total 

 preparations made from bass worms, but sections of similar imina- 

 ture individuals show the follicles with their thin wall enclosed 

 cells whose structure is then identical in appearance with that of 

 the immature germinal cells of the testes and ovary. In sections 

 from mature worms the follicles contain similar immature cells 

 and also fully formed yolk cells with large nucleus and nucleolus 

 and a cytoplasm containing granules, some of them measuring 

 0.001 mm. in diameter. These are food granules; in producing 

 them the follicle cells differ from ovarian cells with which they 

 are very likely homologous. 



