206 



Mr. F. S. Conant on the Chcetognaths. 



evidence ('Circular,' no. 119, June 1895). In this form it 

 was found that the two " ovisperra ducts " were united by a 

 transverse branch, a structure that would seem to have no 

 significance in an oviduct, but would be extremely useful in 

 uniting two receptacula seminis, inasmuch as a single copula- 

 tion, affecting only one side, would thereby serve to fertilize 

 the ova of both sides. 



It would seem, then, that the female reproductive system of 

 S. hispida (and, perhaps, all Chaitognaths) consists on each 

 side of the ovary, the receptaculum seminis, and a temporary 

 oviduct lying parallel and internal to the receptaculum and 

 uniting with it posteriorly to open on a common genital 



Fig. 3. 



Fig. 4, 



"MO 



.OB 



Fig. 3. — Cross section of Sagitta hispida, with eggs in the oviduct, before 

 laying. G E, germinal epithelium ; O D, oviduct ; O V, ovum ; R S, 

 receptaculum seminis. 



Fig. 4. — Diagrammatic optical section of the head and neck of S. hispida 

 from above. MO, mouth ; OE, oesophagus ; D, diverticula ; /, in- 

 testine. 



papilla. A more detailed account of the histology of these 

 structures could be given were it not that the Chsetognaths 

 offer such very unfavourable material for the study of micro- 

 scopic anatomy. Kleinenberg's picro-sulphuric, Perenyi's, 

 and corrosive acetic give the best results ; but even with them 

 the objects are very unsatisfactory, and especially so during 

 the processes of egg-laying, when the tissues are evidently 

 being subjected to great stress. 



The exact point at which the spermatozoa come in contact 

 with the eggs I have not been able to determine. Grassi 

 says that spermatozoa can pass into the ovary, where he has 

 found them ; but he does not state that fertilization occurs 



