The Germ-cells of Lophius. 565 



Prof. J. S. Kingsley, of Tufts College and to Prof. H. V. Wilson 

 of the University of North Carolina. 



I. Review of the Literature 



1. The Origin of the Germ-cells 



A study of the literature shows that there are three quite dis- 

 tinct views about the origin of the germ-cells of vertebrates, viz., 

 (a) theory of the germinal epithelium, (b) the gonotome theory, 

 (c) the theory of early segregation. There have also been a 

 few writers who have held that the germ- cells arise by a combina- 

 tion of two of these processes. 



a. Germinal epithelium. This view is due to Waldeyer ('70). 

 In the embryos of various vertebrates, he first recognized the 

 germ-cells as large rounded cells in the cylindrical epithelium 

 covering, the genital ridge. He considered that the cells arise 

 by the transformation of the cells, among which they are observed. 

 This region of the peritoneum has since been known as the 'germ- 

 inal epithelium.' To the rounded cells observed here, he gave 

 the name 'Ureier' (primordial ova) because he believed that 

 the ova, but not the spermatozoa came from them. These latter 

 he considered had their origin from the epithelium of the Wolffian 

 duct. Later ('03) he had come to recognize that the spermatozoa, 

 as well as the ova arose from the 'Ureier' so that he spoke also 

 of 'Ursamenzellen.' 



This view of the origin of the germ-cells was at once accepted 

 by embryologists, and by far the greater number of writers from 

 that time to the present have held this view. This explanation 

 so readily fell in line with the observations, that its accuracy 

 was taken for granted by most writers without careful research 

 to test it rigidly. 



So many have been the papers describing such an origin, or 

 assuming it, and the subject has been so often reviewed that it 

 is unnecessary to give special notice to those papers. Many of 

 the more important ones are listed in the Bibliography. 



JOURNAL OF MORPHOLOGT, VOL. 21, NO. 4. 



