284 



N. M. Stevens. 



This was very likely due to the abnormally slow passage of the 

 egg under laboratory conditions. 



Both living material and sections show that the sperm-duct 

 and oviduct are entirely separate for their whole length, each 

 having its own opening to the exterior. By exerting pressure 

 on the cover-glass, a stream of sperm was forced out of the mouth 

 of the sperm-duct when the oviduct, including its sphincter-like 

 pore, was entirely closed. This is shown in Fig. E, an optical 



Fig, G. Longitudinal section of an egg in the oviduct. 



section of the sperm-duct with its external opening, and the walls 

 of the oviduct adhering to the sperm-duct as they normally appear 

 except when eggs are being discharged. In Fig. F, a camera 

 drawing from a longitudinal section of Sagitta elegans, the same 

 conditions are shown. The sperm-duct (sd) is here much enlarged 

 but empty, and the oviduct (od) wall shows a characteristic 

 fold which opens, in part at least, when an egg passes. In Fig. 

 G, the sperm-duct contains spermatozoa and the oviduct is being 

 opened up by an advancing egg (o), which pushes apart the sperm- 

 duct and the anterior wall of the oviduct. An air-space (a) 

 appears here as in the living material. 



