The cellular elements of the Ovary of Platyphylax designatus Walk. 215 



Claus (6) gave, many years ago. a clear Solution of the problem; 

 to this Short list might be added many more. These views have 

 not been held by all and there have also been many who have given 

 different ones as to the origin of oöcyte, nurse and epithelial cells. 

 At present the question is that concerning the origin of the epithelial 

 cells; do the cells, as many believe, all have a similar origin, or do 

 these originate differeutly than do the oöcytes and the nurse-cells, 

 Heymons (18), GiAEDiNA (8), Gross (11). 



It seems hardly necessary to enter here into a review of the 

 work which has been done on the later maturation of the egg and 

 the subject of tetrad formation. In neither of the cells which here 

 in Platyphylax form paired chromosomes and have a rather doubtful 

 tetrad formation, has the work been carried on to the following 

 division. This in the nurse-cells would of course be impossible as 

 they do not again divide, and their history, where we leave it, is 

 almost ended. With the oöcyte one would have to carry on the 

 observations through the formation of the polar bodies, a work we 

 have not undertaken. The tetrad formation is in Platyphylax rather 

 doubtful, some of the paired chromosomes undoubtedly breaking up 

 without passing through this stage or, if reached, it is only one step 

 in their disintegration. Our account of their formation is, in general, 

 similar to that of Rückert, Hacker and vom Rath. 



Historical. 



Very few groups of insects have received less attention from 

 entomologists than have the Phryganeidae, and when one endeavors 

 to find papers treating of the anatomy or histology of the reproduc- 

 tive Organs, there is very little to be found. The only papers I have 

 been able to find which, in this group of insects, would be of any 

 comparative interest with our subject are those by Brandt (3), Stuhl- 

 mann (36) and Stitz (34). 



Brandt's (3) work has here and there a mention of the ovary 

 of Holostomis phalaeizoides , the principal caddis-fly he studied; he 

 was unable to find an epithelial layer around that part of the Chamber 

 in which were the nurse-cells, and noted, correctly, that these same 

 cells become spindle shaped around the old oöcyte. His figure of 

 an ovarian tubule of Holostomis shows very little cellular structure. 

 At one place he says »An den voluminösen und grobkörnigen Dotter- 

 bildungskeimbläschen von Holostomis konnten die Keimflecke weniger 

 tiberzeugend zur Anschauung gebracht werden.« 



