ANNELID GENUS CAMBARINCOLA — HOFFMAN 289 



of the prostate back into the spermiducal gland, so that all remaining 

 of it in existing species of that genus is the bulbar tip, occuiTing as 

 a protuberance on the dorsal side of the gland near its ental end. 



Ejaculatory duct. The spermiducal gland discharges to the outside 

 through a tubular duct with distinctly muscular walls which is un- 

 doubtedly capable of spasmodic or peristaltic action, and which is 

 appropriately named the ejaculatory duct (Holt, 1949). Both the 

 structure and distribution of this duct vary greatly in the famih^ 

 In certain genera (e.g., Xironogiton) , it is quite thin-walled, probabl}^ 

 the primitive condition. In at least one undescribed species referable 

 to Xironodrilus in the sense of Ellis, it is absent altogether. In 

 Cambarincola macbaini (for which a new genus is being proposed 

 elsewhere), it is greatly enlarged and filled with a mass of convoluted 

 tubing. From the morphological standpoint, the duct is simply a 

 segment of the main sperm conducting passage; we should therefore 

 expect the least modified condition to reflect the generalized or 

 primitive state. Insofar as Cambarincola in the strict sense is con- 

 cerned, the ejaculator}^ duct is basically similar through all the species — 

 of about the same proportionate length and with a moderately muscu- 

 lar wall. Ectally it merges gradually into the penial sheath of the 

 bursa. 



Bursa. This, the outermost differentiated portion of the male 

 reproductive system, is fundamentally a muscular invagination of 

 the ventral body wall — mvaginated to permit concealment of the 

 penis well withm the body, and muscular to achieve extrusion of the 

 penis during copulation. The accompanjang illustrations (figs. 3 

 and 4) afford some idea of the composition of the bursa, which is 

 divided into two major anatomical parts: the penial sheath and the 

 atrium. 



In virtually all branchiobdellids the biu-sa is a subglobose to pyri- 

 form organ openmg to the exterior at the midventral part of segment 

 VI. Typically it projects mesad into the coelom or is directed some- 

 what caudad. Its ental half is taken up largely by the penial sheath 

 (fig. 3, PS) which is the somewhat differentiated muscular area 

 surrounding the ectal end of the ejaculatory duct and the virtually 

 continuous penis. The latter is very variable in structure through 

 the family, taking the form of a simple truncate cone which terminates 

 the ejaculatory duct, or becoming gradually modified into a much 



of the spermiducal gland; B, bursa; EB, ental bulb; ED, ectal duct; EJD, ejaculatory 

 duct; EP, ental process; P, penial part of bursa; PDD, posterior deferent duct; PDL, 

 posterior deferent lobe of the spermiducal gland; PR, prostate gland; PS, penial sheath 

 of bursa; SDG, spermiducal gland. The lower case letters a-d in figures 3 and 4 are 

 located at the same anatomical position in both drawings. 



