479 



out, that, just as "dermoids" or embryomas may occur in places other 

 than the ovary or testis, so also primary germ-cells, from which they 

 must have arisen, are now for the first time recorded as present in 

 like situations, other than in the "sexual glands". 



Prof. Wilms in a letter to the writer remarks, that naturally he 

 has no hope or wish to carry back any of the embryomas to the 

 polar bodies, that is to say, to trace out the whole course of their 

 individual abnormal development. This impossible task will, perhaps, 

 be rendered needless by the discovery of the existence of vagrant or 

 lost primary germ-cells. 



These must represent in an actual tangible form the hypothetical 

 "verirrte Keime" of the pathologists. 



It is not from secondary germ-cells, or from germ-cells, which, 

 having taken on the characters of eggs, have given off one or both 

 polar bodies, that such embryomas can arise. Wilms' discoveries and 

 mine, even taken along with Emanuel's^) recent speculations, afford 

 no evidence of the existence of parthenogenesis among the Vertebrata. 



Neither a conjugation of germ-cells, nor a parthenogenetic devel- 

 opment of such is needed to account for the dermoids. It is true, 

 that Wilms has not followed his embryomas back to the "egg"; 

 but he has shown, that, if regarded as abnormal embryos — which 

 may manifest themselves in childhood, adult life, or even in old age! 

 — all the peculiarities of their structure are explained. 



In the same way it may be truly said of my researches, that 

 only the existence of vagrant primary germ-cells is established, and 

 not their spontaneous development. The reply is not to seek. If they 

 ever do develop, the tumours, known as dermoids or embryomas are 

 their only products. No normal development of them can take place ; 

 and no other proof of the possibility of their abnormal development 

 can be given, other than that afforded by a tumour, a dermoid or 

 embryoma. 



To my researches those of Wilms furnish the complement re- 

 quired; and it is, perhaps, not too much to say that my work, although 

 carried out in fishes, and not in man or mammals, furnishes his re- 

 sults with the one link needed to complete the chain. 



Although the writer is convinced, that vagrant primary germ- 

 cells occur in the development of even the highest Vertebrates, he is 



1) E. Emanuel, Zur Aetiologie der Ovarialdermoide. Zeitschr. f. 

 Geburtsh. etc., Bd. 42, 1900, p. 302—315. 



