Tin- gcrm-cclls. C)9l 



they ariso before there is any embryo at all. Inst(!n(l of being cells 

 of a younger generation thiui tJK! embryo, as they would Ix; if (l(Ti- 

 vatives of a genninal ei)ithc]iuin, they are in reality up to ji, certain 

 point of the lik(! generation. 'I'hey arc; ,sister-C(!lls of the (îrnbryo — 

 ''(J(!sdiwist<!r" with it, to use a German phrase, for whieli there is no 

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

 embryo. 



After prolonged and careful investigation of the origin and early 

 history of the i)rimiiry germ-cells of liaja, conducted iifter the best 

 and most exact methods, it must be em|)hatically stated, that in this 

 animal there is no particle of evid(!nce to be found, pointing to an 

 origin of a single germ-cell from any c(;ll or cells of the embryo. 



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

 among others Skmon ('87) sp(!aks so confidently without figuring a 

 singhî one, are in the skate *) only conspicuous by tot;il absence. iJad 

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

 unique acquaintance with such transitional cells in the cases of 

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

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

 vestigator, 



'J'he change from epith(!lial cell to germ-c(;ll, though asserted 

 times without number, has never really been depicted, and in ;i,ll j)rob- 

 ability it has never actually been observed. Indeed, it does not (;xist. 



Born in his review speaks of the overwhelming testimony of 

 research jis in favour of Waldkykk's view. 'J'his is not tin; itn[)ression, 

 wliich a study of the literature has made on my mind. IiALF()(jk's 

 and Skmi'kk's classic researches go to show the complete a,bs(!nc(! of 

 genetic relationship b(!tween germinal (îpithelium and germ-cells. l>oth 

 investigators certainly accepted Waldkyku'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 pujiil of his the 

 l)uyment of a tribute of admiration to Semi'eu's really classic r(!searches 

 on the; urinogenital system of F.lasmobranch fishes. Th(;y form now, 

 more than 25 years after he wrote them, the foundation of our know- 

 ledge of this system in Vertebrate animals. They an;, and will prob- 

 ably long remain, among the finest inv(;stigations in Vert(;brate em- 

 bryol(')gy ever carried out. Only those, who wen; [)rivileged to know 

 bEMi'EU, are aware at what cost! 



1) And in tlio chick also. Compare, further, Ni/hhkatm (1901). 



