ANNELID GENUS CAMBARINCOLA — HOFFMAN 287 



lobes are called anterior or posterior deferent lobes according to the 

 position of the deferent ducts which enter them. The posterior 

 ducts collect spermatozoa from the sixth segment, the anterior ducts 

 from the fifth. 



Prostate gland. This tubular structm-e is the "accessory sperm 

 tube" of Ellis and other workers, but its function is almost certainly 

 at least analogous to that of the prostate gland in other animal 

 groups. Anatomically it originates at the junction (in most cases) 

 of the spermiducal gland and the ejaculatory duct, and extends 

 entally along the gland, both closely invested with a common (peri- 

 toneal) membrane. The histology of the prostate varies considerably. 

 In some species it is superficially almost identical with the spermiducal 

 gland in appearance, as regards both the size and apparent compo- 

 sition of the cells. In others there is a remarkable difi^erence, one 

 visible even under low power magnification, in that the prostate is 

 made up of very large vacuolated cuboidal epithelial cells apparently 

 with little or no secretory contents. 



The actual size and shape of the prostate gland varies to a con- 

 siderable extent, chiefly in diameter and length with respect to the 

 spermiducal gland, and this variation is often of considerable diag- 

 nostic importance. It is of com^se necessary to make certain that 

 the true dimensions are determined by a careful observation — the 

 prostate is often partially concealed or its ental end tm'ned away 

 from the major axis, creating a much foreshortened effect. In at 

 least one case, the diameter of the prostate in comparison with that 

 of the spermiducal gland provides the major basis for separation of 

 two species of the genus. 



Entally the prostate ends blindly, although in the group in which 

 it is histologically distinct from the spermiducal giand, there is a 

 terminal development in the form of a clear bulb generally about 

 the same diameter as the prostate proper, but occasionally somewhat 

 rudimentary (in primitive species) or quite enlarged in specialized 

 forms. The relationship of terminal bulb to vacuolated epithelial 

 cells is so constant that the one is prima facie evidence of the other 

 even when conditions prohibit du'ect observation of both! 



Within the family Branchiobdellidae, the prostate gland apparently 

 typifies the group of genera clustered around Camharincola and may 

 therefore serve a useful purpose as a tribal or subfamilial character. 

 It is considered to be, in its simplest form, an outpocketing of the 

 spermiducal gland which has, in the course of evolution, become 

 histologically differentiated and altered in size and shape (from a 

 broad short process to a long, slender, tubular one). I suspect that 

 in at least one specialized branch of this part of the famUy, that which 

 has produced Ceratodrilus, the tendency has been toward consolidation 



653871 — 63 2 



