The germ-cells. 687 



A full account of von Jhering's paper, which is in a very acces- 

 sible journal (as well as in: Arch. Anat. Physiol., 1886, p. 743 — 750) 

 would take up too much time and space. Let it suffice, that the author 

 clearly recognised the full significance of his finds on general problems 

 of embryology, like-twins, and the mode of the development. 



This paper is now 15 years old ; but, so far as the writer is 

 aware, no account of the contained finds has found its way into 

 any text-book, and without doubt the discovery, which has 

 been neither refuted, nor accepted, has passed without 

 influencing scientific opinion at all! 



Its author had at least the reward, mentioned by a recent 

 writer 1), that "he will thereby attain the fame of all true scientists, 

 of being thoroughly disbelieved when he writes the truth". 



With the unfolding of an embryo, and almost from the com- 

 mencement of this, there begin the wanderings of the primary germ- 

 cells into it. This process, as already insisted, is exactly comparable 

 to the migrations of the germ-cells of a Hydrozoon from an asexual 

 stock either into the developing "sexual person" or into the site of 

 its formation. 



Finally, the germ-cells themselves remain to be considered. That 

 these are unicellular organisms, passing one part of their life-cycle 

 in a sterilised individual, the Metazoon, formed by one of them, is 

 clearly enough laid down in preceding pages. 



For the animal kingdom at least this idea seems to entail a com- 

 pletely new conception of the nature of a Metazoon and of the relative 

 rôles of it and the germ-cells. Admittedly, the original stock, from 

 which the Metazoa developed, were unicellular forms. Perhaps too, 

 it may be accepted as certain, that the majority of zoologists and 

 embryologists regard the formation of "sexual products", eggs and 

 sperms, as a "reversion" to this Protozoan ancestral type. 



This latter appears to be quite erroneous, and there is all the more 

 satisfaction in revealing its fallacious nature, in that like some other 

 groundless dogmas of embryology, it is at its basis a survival of the 

 Naturphilosophie, according to Oken. 



In dealing with embryological and other problems it is well to 

 regard them from every side, not forgetting the inside also. Since 

 Oken's time, if not before it, embryologists have been true to their 



1) Words by an Eye witness, by "Linesman", p. 317, 1901, Black- 

 wood, London and Edinburgh. 



