11 



I have not been able to bring my observations into harmony with 

 the theory of Nussbaum, according to which all the ova are derived 

 from »Geschlechtszellen«, independently of the germinal epithelium ; 

 nor have I succeeded in finding any evidence of the view recently put 

 forward by V al a o rit is, who refers the origin of the ova to white 

 blood-corpuscles . 



As to the mode of origin, my observations appear to warrant the 

 following statements. 



It is in the crowded areas (»cell-islands«) that we meet with what 

 1 have called germ-cells, which lie at first in the germinal epithe- 

 lium, and are plainly a part of it. That the germ-cells lie in, and yet 

 differ from, the ordinary cells of the germinal epithelium, is a fact 

 which, by itself, might be interpreted in favour of Nussbaum's 

 theory. But these germ-cells arise from the ordinary cells of the epi- 

 thelium. 



During the winter months epithelial cells were found whose nuclei 

 were in process of division, and others in which the division was al- 

 ready completed. In cells having two nuclei, these nuclei were some- 

 times alike, and like the nuclei seen in other epithelial cells ; while in 

 other cases one nucleus differed in one or more particulars from the 

 twin nucleus. In such cases, one nucleus always retained the aspect 

 (treated in nitrate of silver) of the ordinary epithelial nucleus, while 

 the other varied from this in being larger, more nearly spherical, more 

 coarsely granular, and darker. The latter becomes the nucleus of a pri- 

 mary germ-cell, which appears to be formed within the parent cell, and 

 to get liberated from it by out-growing it. As the nucleus enlarges, an 

 envelope of protoplasm, derived from that of the parent cell, becomes 

 marked off", but without the formation of any distinct membrane. The 

 germ-cell grows larger, tends more and more to expand beyond the 

 limits of the original cell, begins to jut a little under a neighbouring 

 cell, and sinking deeper, finally becomes an independent cell, sur- 

 rounded on all sides with epithelial cells , which have no definite 

 arrangement. 



In regard to the origin of the follicular epithelium, I have ob- 

 tained no decisive results; but what I have seen seems to me to favour 

 the opinion that it is formed directly from the epithelial cells which 

 cluster around the germ-cell. In this case, the germ-cell would repre- 

 sent the primordial ovum. 



The first plain indication of the presence of yolk-spherules appears 

 about the time the egg has attained a diameter of 0,25 mm. The proto- 

 plasm has become somewhat clouded with very minute granules ; and 

 scattered patches, consisting of larger or smaller aggregations of small 



