324 Beard, Heredity and the epicycle of the germ-cells. 



bryo, before this had undergone histological differentiation. In urging 

 this Nussbauni really took up a very moderate attitude. To refute 

 his argument from the botanical side, it is necessary to compare the 

 conditions in the corresponding generations in the two kingdoms, that 

 is, to place the embryo and the prothallus together, not the embryo 

 and the sporophyte. It should also be pointed out, that even now the 

 early history of the germ-cells of ,,most animals" has as yet been 

 very inadequately investigated. Where it has been traced back to the 

 farthest possible point, there a very early origin has been invariably 

 made out. This is now so in Moina, Cyclops, Ascaris, Strongylus, 

 Cecidomyia, Chirouomus, Sagitta, Phalaugium, Lernaea, Micrornetrus, 

 Scorpions (Brauer), several insects (Heymons) ; some sponges (Ma as), 

 and Cephalopoda (V. Faussek), and, lastly, in Pristiurus (Rabl), 

 Scyllium, and Raja. 



Hitherto the apparent phenomena in the Vertebrata stood in the 

 way. Here even a segniental origin of the ,,sexual cells" had been 

 recorded in relatively late stages. This is, however, only one of the 

 ever recurring instances of the earliest observed appearance of a thing- 

 being taken to represent its first origin. This is only permissible in 

 embryological research, when an earlier origin is absolutely out of question. 



From a fair acquaintance with tlie embryological literature treating 

 of the germ-cells and their origin the writer must maintain, that there 

 is really no reliable evidence, pointing to the very late appearance of 

 the germ-cells in any single case. On the other hand, there is a 

 steadily accumulating body of strong testimony in favour of their 

 early separation off in many different divisions of the animal 

 kingdom. Even the case of the Hydroid polypes cannot be cited in 

 disproof, for Weismauu's own great researches reveal not so much 

 the origin of the germ cells in these as their remarkable migrations. 



In saying the foregoing in face of the known facts concerning 

 Moiua, the Dipterous insects, etc., Weismann defined not only his 

 own standpoint towards the question, but also that of most other 

 zoologists. The exception meets with no favour, until it ceases to be 

 such, and adapts itself to the rule. But ,,die Natur geht ihren Gang, 

 und was uns als Ausuahme erscheint, ist in der Regel". And this is 

 so, simply because what we regard as the rule is often false, the real 

 law being that, with which the apparent exception conforms. 



While only from 2 to 8 primary germ-cells were found very early 

 in the development of this or the other form; while, as in the higher 

 animals, one could study the early development without seeing any 

 gerni-cells - their ,,segniental origin" even being witnessed at later 

 periods - - the good old rule, in plain language, the superstition, that 

 the offspring was formed by the union of a small portion of each of 

 its parents, seemed to be the only logical conclusion. Thus is hap- 



