138 Harry Lewis Wieman. 



1. The Development of the Ovary 



The cell elements of the ovary 



The insect ovary has long been a favorite object for microscop- 

 ical study, yet some of the most important aspects of the problem 

 it presents are unsatisfactorily answered. The organ exists in 

 a wide variety of morphological types, but however great its lack 

 of constancy in macroscopical structure, it always shows in the egg- 

 tube the presence of three elements: germ cells, nurse cells and 

 epithelial cells. One of the questions that has engaged the atten- 

 tion of many investigators is the origin of these cells. 



Following the contributions of Dufour ('33, '41) and others on 

 the gross anatomy of the insect ovary. Stein ('47), in his mono- 

 graph on the female genital organsof a large number of Coleoptera, 

 published the results of the first thorough investigation of the 

 histology of the ovary, and thus laid the foundation for all sub- 

 sequent work in this field. He showed that the terminal thread 

 {Endfaden) is not a blood vessel as had been stated years before 

 by Johannes Miiller ('25), but that in all probability it serves as 

 a suspensory ligament which binds the ovarioles together and 

 fixes them to the dorsal wall of the thorax. The eggs, he believed, 

 arise from the large cells in the lower or proximal part of the term- 

 inal chamber, and that the cells in the other part of the tube are 

 the yolk-building elements, i.e. , nurse cells. He correctly described 

 the two sheaths of the ovary, the outer "peritoneal Hillle" and 

 the inner structureless "tunica propria.^' To the germinal vesicle 

 he attributed the morphological value of a cell, and judging from 

 more recent work, he also erred in considering the chorion of the 

 egg a result of the fusion of follicle cells, instead of a secretion pro- 

 duct of these cells, as later research has demonstrated. 



H. Meyer ('49) described two kinds of so-called "nuclei'^ in 

 the ovary of Lepidoptera, small ones of an epithelial nature, and 

 large ones which develop into germinal vesicles, while the nurse 

 cells were regarded as aborted ova. Here then is the first claim 

 for a common origin for reproductive and nurse cells, the epithe- 

 lial cells having a different origin. 



