481 



the embryo, more particularly from the germinal fold of the peritoneum. 

 This doctrine is based on the classic investigations of Waldeyer ('71). 



It is a painful task to attack and attempt the overthrow of a 

 thesis, resting on the authority of a great and celebrated anatomist. 

 Truth, however, must prevail over error. 



There is no germinal epithelium! 



The germ-cells of Vertebrates do not arise from any part of the 

 embryo. They are not products of any organ, of any epithelium of 

 the embryo. The embryo only forms those structures, which make 

 up its own body, which are parts of its soma. The germ-cells are in 

 no sense parts of the soma ^). They are distinct entities, not really 

 necessary for the individual existence of the embryo. In the skate 

 they arise before there is any embryo at all. Instead of being cells 

 of a younger generation than the embryo, as they would be if deri- 

 vatives of a germinal epithelium, they are in reality up to a certain 

 point of the like generation. They are sister-cells of the embryo — 

 "Geschwister" with it, to use a German phrase, for which there is no 

 English equivalent. They are not in any sense the progeny of the 

 embryo. 



After prolonged and careful investigation of the origin and early 

 history of the primary germ-cells of Raja, conducted after the best 

 and most exact methods, it must be emphatically stated, that in this 

 animal there is no particle of evidence to be found, pointing to an 

 origin of a single germ-cell from any cell or cells of the embryo. 



The transition-stages from epithelial cell to germ- cell, of which 

 among others Semon ('87) speaks so confidently without figuring a 

 single one, are in the skate only conspicuous by total absence. Had 

 they existed, they would have been seen; for the writer can claim a 

 unique acquaintance with such transitional cells in the cases of gan- 

 glion-cells and leucocytes. Probably he has seen more transitional 

 cells, leading to these two latter kinds of cell, than any other in- 

 vestigator. 



The change from epithelial cell to germ-cell, though asserted 

 times without number, has never really been depicted, and in all 

 probability it has never actually been observed. Indeed, it does not 

 exist. 



Born ('95) in his review speaks of the overwhelming testimony of 



1) Originally "as Weismann has insisted" was here written, but a 

 renewed reference to his works showed, that in many cases at least he 

 had maintained an origin of germ- cells from somatic cells. 



Anat. km. XVIII. Anfsatze. 31 



