482 



research as in favour of Waldeyer's view. This is not the impression, 

 which a study of the literature has made on my mind, Balfour's 

 and Semper's ckxssic researches go to show the complete absence of 

 genetic relationship between germinal epithelium and germ-cells. Both 

 investigators certainly accepted Waldeyer's view, but it would be 

 difficult to cite from their researches a single observation really sup- 

 porting it. 



At this juncture it may be permitted to an old pupil of his the 

 payment of a tribute of admiration to Semper's really classic re- 

 searches on the urinogenital system of Elasmobranch fishes. They 

 form now, 25 years after he wrote them, the foundation of our know- 

 ledge of this system in Vertebrate animals. The are, and will prob- 

 ably long remain, among the finest investigations in Vertebrate em- 

 bryology ever carried out. Only those, who were privileged to know 

 Semper, are aware at what cost! 



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 Waldeyr's 

 standpoint. 



Rückert's reference of 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 RücKERT, 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, Koelliker, and Nagel. Mihalkovics occupies a 

 peculiar position. He asserts, that the so-called "primitive ova" pro- 

 duce no sexual elements, and the origin of these he refers to the 

 germinal epithelium. 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 



