FURTHER STUDIES ON REPRODUCTION IN SAGITTA 



N. M. STEVENS 

 Bryn Mawr College, Bryn Mawr, Pa. 



With One Hundred and Two Figures 



Inteoduction 



In March, 1905, it was my privilege to avail myself of the oppor- 

 tunity offered by the newly opened winter quarters of the Marine 

 Biological Laboratory at Woods Hole, Mass., to make a further 

 study of the method of egg-laying in Sagitta elegans. A recent 

 paper ('05) had described, as fully as was possible from fixed ma- 

 terial alone, the later stages in the ripening of the ovum and its 

 entrance into the oviduct which is temporarily opened up between 

 the sperm-duct and the median oviduct wall. Questions arose as 

 to the relation of the two ducts at the point of opening to the ex- 

 terior, and also as to the activity or passivity of the ovum in 

 its passage from the ovary to the reproductive pore. 



Hertwig ('80) in ''Die Chsetognathen," (pp. 52-54 and PL 4, 

 Fig. 13), describes and figures the sperm-duct as the oviduct, 

 and the oviduct wall as the 'Keimlager.' He observed hving 

 spermatozoa in the 'oviduct' but never in the ovary. Finding 

 no opening from the ovary to the duct, he concluded that the 

 eggs when ripe must enter the duct at its posterior end, and that 

 the anterior portion of the observed duct must serve merely as a 

 'Samentasche.' This duct had been previously described by 

 Krohn ('53) and by Leuckhart and Pagenstecher ('58) as a 'Sam- 

 entasche' Kerferstein ('62) also saw spermatozoa in this canal, 

 but nevertheless regarded the whole of it as an oviduct, and was 

 of the opinion that there must be an anterior opening from the 

 ovary into the oviduct. Grassi ('83) called the duct a sperm- 



JOURNAL OF MORPHOLOGT — VOL. 21, NO. 2 



