280 N. M. Stevens. 



oviduct, but did not discover by what method the eggs escaped 

 from the ovary. 



In two brief papers ('03, '05) I have shown that the duct 

 described by previous investigators of Sagitta, is a sperm-duct 

 (Samentasche), or sperm-receptacle, lying within the oviduct 

 which is closed except when ripe eggs are being discharged. 

 ('03, Figs. 1-3; '05, Figs. 1, 11, 12). The ' Keimlager ' of Hertwig, 

 which forms the wall of the oviduct, I had suspected was not 

 germinal epithelium at all and therefore not a part of the ovary 

 proper, or only an accessory structure to be classed with the sperm- 

 duct and the endothelial membrane covering the ovary, and not 

 with the germ cells. This was one of the points which led to 

 further investigation of the reproductive system of Sagitta. 



Observations on Living Material 



Through the kindness of Mr. George M. Gray, curator, I was 

 able to sample the Sagitta material at intervals during March, 

 1905, and thus to time my arrival at Woods Hole when the laying 

 season was just beginning. 



The tim.e of day when Sagitta elegans discharges its eggs is not 

 as definite as in the case of Sagitta bipunctata. The latter lays 

 about sundown, while the former has been observed to discharge 

 its eggs at various times between 11:00 a. m. and 6:00 p. m., 

 and there is no reason for thinking that the eggs may not be laid 

 at any other tim.e in the twenty-four hours. 



In Sagitta collections brought in at about 9 :00 a. m. all stages 

 of egg-ripening were found in different individuals. The nuclear 

 membrane disappears from 15 to 30 minutes before the egg begins 

 to push its way into the oviduct. That the egg does actively push 

 its way between the oviduct wall and the sperm-duct, and by its 

 own contractions or by shifting of material within the egg-mem- 

 brane, make its way down the oviduct to the reproductive open- 

 ing, I have no doubt, after observing the process in many individ- 

 uals. 



Fig. A is a freehand sketch' from a living Sagitta under a low 

 power of the compound microscope, showing five eggs entering 



