396 University of California Publications in Zoology. [VOL. 6 



receptaculum seminis by a small median portion. They are com- 

 posed of numerous rounded follicles, from which run collecting 

 tubules to empty into five main oviducts, one posterior, two 

 lateral and two anterior ducts. These lead into the receptaculum 

 ovorum, which is embedded in a mass of loose tissue in a depres- 

 sion on the anterior dorsal surface of the receptaculum seminis. 

 The receptaculum ovorum (rec. ov., pi. 45, figs. 73, 75), is 

 about 3 mm. in its antero-posterior and its dorso-ventral diam- 

 eter and about 6 mm. in transdiameter. These measurements are 

 the average for several sexually mature worms. 



The vitellaria are composed of loosely-grouped follicles, each 

 containing ten or fifteen cells, lying just within the inner trans- 

 verse musculature and outside the inner longitudinal. The fol- 

 licles are present throughout the body with the following excep- 

 tions : (1) dorsal and ventral to the uterus, that is, in the median 

 third of the body in the two middle quarters or more of its 

 length; (2) anterior to the posterior border of the acetabulum; 

 (3) posterior to the level of the ventral canal opening. 



The lateral folds are densely supplied with vitellarian fol- 

 licles, these forming the greater part of the folds. The ducts 

 of these yolk glands unite into four main lateral ducts, which 

 empty into a yolk reservoir, or "Endstiick, " which lies in the 

 dorsal depression of the receptaculum seminis above mentioned, 

 just posterior to the receptaculum ovorum. It gives off a single 

 efferent vitellary duct, which enters the afferent oviduct, as 

 described below, a short distance back of the entrance of the duct 

 connecting the efferent oviduct with the receptaculum seminis. 



The efferent yolk-ducts (pi. 39, fig. 42, vit. d.), appear in 

 stained and cleared preparations as a dark brown anastomosing 

 network of delicate threads, spread over the receptaculum 

 seminis and the first three or four coils of the uterus, and con- 

 verging to the yolk-reservoir in the concavity of the recep- 

 taculum. 



From the ventral surface of the receptaculum ovorum is 

 given off in the median line a single efferent duct (ef. ovd.) 

 which receives first a short thick-walled duct from the recep- 

 taculum seminis (duct, sem.) ; and then an efferent duct from 

 the yolk reservoir (ef. vit.d., pi. 45, figs. 71-74). This duct 



