EFFECTS OF AMPHIMIXIS ON THE GERM-PLASM 245 



the new organism,* we may conclude from certain phenomena 

 of heredity that the reduction of the number of ids to one half 

 does not result in the separation of groups of ids which are 

 always the same, and are definitely determined beforehand, but 

 in the removal of different groups on different occasions. The 

 gertn-cells of one and the same organisfn must cofisequently coft- 

 tain very different combinations of ids, and consequently also 

 of prijnary constituents., than those which were present in the 

 parents of this orgatiism. The reduction affects the paternal 

 and maternal idants in a precisely similar and equal way ; it 

 takes place in such a manner that any combinations may result 

 from the halving of the number of idants. Let us take, for in- 

 stance, four idants a + b and c + d ; not only may the paternal 

 group a + b and the maternal group c + d, as well as combina- 

 tions of a + b and c + d, be present in the fully-formed germ-cell, 

 but also the combinations a + c and b + d, or a + d and b + c, — 

 that is to say, combinations each of which consist of one paternal 

 and one maternal element. 



A moderate amount of difference between the germ-cells of 

 an organism as regards their contained primary hereditary con- 

 stituents will thus result. In the case of the four idants taken 

 above as an example, only six combinations would be possible, 

 and consequently there could only be six kinds of germ-cells 

 differing from one another in respect of their primary constit- 

 uents. The number of possible combinations, however, in- 

 creases very considerably with the increase in the number of 

 idants; for example, 70 combinations are possible with eight 

 idants, 12,870 combinations with sixteen idants. 



* Appearances certainly seem to contradict this assumption, and I am 

 fully aware of the fact that Oscar Hertwig, and more recently Guignard, 

 have stated their opinion to the contrary. In many conditions of the 

 nucleus it is, in fact, impossible to recognise the idants, and they certainly 

 do not exist as such, — that is, in the form of compact rods. But it is quite 

 conceivable that the connection of the ids in an idant may nevertheless 

 persist, and that the individual ids are connected together by fine threads 

 of ' linin.' An observation made by my assistant, Dr. Hacker, supports 

 this view. He noticed that the microsomes of the rod-like idants of the 

 growing tgg in Copepods become separated from one another, but always 

 remain connected by a delicate thread of linin, which in this instance can 

 be stained : the linear arrangement of the microsomes certainly persists in 

 this case. {C/. Hacker, ' Die Eibildung bei Cyclops und Canthocamptus,' 

 Zool. Jahrbiicher, Abth. f. Anat. und Ontog., Bd. v., p. 237.) 



