1 78 J. THOMAS PATTERSON. 



Posteriorly the atrium is directly continuous with an enlarged, 

 rather thick-walled uterus, which in turn gives rise to a duct-like 

 structure that extends backwards and upwards (Fig. 5, ). 

 At the point where these two parts join, the uterus receives the 

 small ducts of the many unicellular shell-glands (Fig. 1,5). 



Towards its distal end the uterus bifurcates, sending a branch 

 to each of the bilaterally arranged ovaries (Fig. 3). The bi- 

 furcated part of the uterus serves as a receptacle for spermatozoa 

 a condition that is not entirely unique for this species and 

 also performs the function of insemination. On account of the 

 backward and upward course taken by the uterus, the two distal 

 parts come to lie just below the ventral surface of the intestine, 

 at a place slightly posterior to the middle point of the body 



(Fig. 5)- 



The development of the uterus has not been studied and I 

 can not therefore state with certainty the exact nature of this 

 organ. Slightly posterior to the point where the proximal and 

 distal parts join the duct is frequently very indefinite and difficult 

 to trace. This, together with the fact that small yolk cells are 

 frequently found within its cavity (Figs. 4, 5) has led the writer 

 to believe that the distal part of the uterus is the product of 

 fusion between the ducts coming from the reproductive glands 

 and therefore should probably be called the oviduct. 



The female reproductive glands consist of a paired " germarium " 

 and a paired "vitellarium," the two glands on each side being so 

 closely associated that the compound structure might properly be 

 termed a "germ-vitellarium." The ovarian portion occupies 

 the anterior part of the body, while the yolk glands occupy the 

 posterior half mainly. 



The clearest idea of the relation of these various parts to each 

 other and to the reproductive ducts can best be gained in a study 

 of horizontal sections which pass just below the ventral side of 

 the intestine. In such sections the ovary on each side is seen to 

 begin slightly anterior to the seminal vesicle, and tx> increase 

 gradually in diameter in passing backwards until it reaches the 

 region occupied by the distal end of the uterus. Here it spreads 

 as a fan-like structure, with ilu- inner margins of the ova con- 

 verging to meet the tip of the uterus (Fig. 4). In composition 



