1910-11.] Development of Germ Cells in Mammalian Ovary. 151 
VII. — The Development of the Germ Cells in the Mammalian 
Ovary, with special reference to the Early Phases of 
Maturation. By A. Louise M c Ilroy, M.D., D.Sc. (From the 
Physiological Laboratory, University of Glasgow.) Communicated 
by Professor Noel Paton. (With Six Plates.) * 
(MS. received June 1, 1910. Read July 4, 1910.) 
Part I. — Introduction. 
Although much literature has been published on the minute anatomy of 
the ovary, there are many controversial points remaining, and therefore 
the publication of the results of the examination of various mammalian types 
adds additional proof to the facts already stated by embryologists. Three 
years ago this work was taken up by me as a preliminary to an investiga- 
tion into the distribution of the chromatic substance in cells which show 
malignant degenerative changes. The work has occupied so much time 
that the publication of the results has been necessarily delayed. In a 
paper on “ Primary Cancer of the Ovary,” published in 1906, I stated, as the 
result of a somewhat limited observation on the later stages of the develop- 
ment of the human ovary, that the cells of the stratum granulosum were 
mesoblastic in origin. This view I have modified by the more thorough 
and extensive investigation of the present paper. 
Part II. — Historical. 
The chief points of interest in the development of the ovary arise from 
the examination of the sex cells after their appearance on the genital 
ridge. Most observers are in agreement with the work of Waldeyer (28), 
who traced their early development from two thickened ridges of 
epithelium on the mesial aspects of the Wolffian bodies. The mode of 
implantation of these cells upon the peritoneum is still in doubt, some 
authors having traced the evolution of the sex cell from the peritoneal 
cell (Pfltiger (19) and others), thus giving it a somatic origin. This theory, 
however, is not held by the majority of observers: the generally expressed 
opinion among recent writers is that the sex cells are differentiated at a 
very early stage, and are laid down while the segmentation of the ovum is 
* The expenses of the research were defrayed by grants from the British Medical 
Association and Carnegie Trust. 
