692 JOHN BEARD, 



Of the workers since then it cannot be said, that they have fur- 

 nished the epithelial view of germ-cell origin with any particular sup- 

 port in fact. Notwithstanding this, no single one of the current text- 

 books on embryology regards the question other than from Waldeyek's 

 standpoint. 



Rückert's reference of the germ- cells to the segmented mesoblast 

 reduces itself to a statement of their supposed segmental distribution ; 

 and, regarded as one of their origin, it is quite unproved and still 

 to be worked out. Moreover, their segmental origin is completely at 

 variance with the facts. As to the term "gono-nephrotome", intro- 

 duced by RücKEßT, Rabl's criticism is strongly reinforced by the 

 facts of the present writing. In face of Rabl's discovery ('96), that 

 but few of them, comparatively speaking, occur in the segmented 

 mesoblast, and my record of far more in other places, the retention 

 of the term becomes needless. This remark applies with even greater 

 force to the expression "gonotome". This as a definite structure is 

 purely a figment of the imagination. 



The authors, who support Waldeyer's view of the origin of germ- 

 cells from epithelial cells are Foulis, Jungersen, Semon, Janosik, 

 Bühler, Kölliker and Nagel. Mihalkovics occupies a peculiar 

 position. He asserts, that the so-called "primitive ova" produce no 

 sexual elements, and the origin of these he refers to the germinal 

 epitheUum. That is to say, he completely reverses the facts. The 

 observations of all these investigators have this feature in common 

 with the original ones of Waldeyer, that they deal with comparatively 

 late stages ; and, therefore, it may be said of them, that they prove 

 nothing whatever as to the first origin of the germ-cells. 



The researches of Nussbaum, Hoffmann, Prenant, Eigenmann 

 and Wheeler all go to disprove any genetic relationship between 

 the germinal epithelium and the "primitive ova" or germ-cells. 



In his recent contribution to the subject Rabl ('96) never refers 

 to either of the above views; but from the circumstance, that he 

 traces back the first germ-cells to embryos of 18 somites, and hints 

 that the possibility of an even earlier occurrence cannot be excluded, 

 his researches furnish no support to the epithelial view, and point, 

 in fact, in the other direction. 



The researches of Nussbaum and others, so far as they go, all 

 favour an origin of germ-cells independently of the tissues of the 

 embryo; or, at any rate, they lend no support to a relationship with 

 any particular tissue or group of cells. Unfortunately these obser- 



