EFFECTS OF AMPHIMIXIS ON ONTOGENY 295 



in a special way in eacli id. It therefore results that the 

 number of homodynamous determinants may vary in the differ- 

 ent stages of ontogeny, and consequently the paternal and 

 maternal hereditary tendencies may preponderate according to 

 the stage or organ under consideration. 



The fact that the offspring may resemble one parent much 

 m.ore closely than the other, is not incompatible with the fact 

 that only half the total number of ids of this parent are present 

 in each of its germ-cells, for all the ids only co-operate when 

 strictly intermediate structures are formed ; but in those cases 

 in which the ids of one parent are overpowered and rendered 

 inactive by a preponderating majority of homodynamous ids of 

 the other parent, the control of the cell is effected by the successful 

 or^do)iiinant' ids. and the others exert no influence. If, there- 

 fore, the determinants of one parent, in very numerous stages 

 of development, preponderate in this manner over those of 

 the other, an instance of apparently monogonic heredity will 

 result, and the offspring will bear a closer resemblance to this 

 parent : and if. moreover, tho 'reducing division ' should happen 

 to take place in one of the germ-cells of this offspring in such 

 a way as to result in those ids which were ' dominant,' and con- 

 trolled the development of this offspring remaining together in 

 the germ-cell, they might possibly preponderate in the next 

 generation over the ids introduced by another parent in the 

 process of amphimixis. 



The problem concerning the possibility of the offspring bear- 

 ing a much closer resemblance to one parent than to the other 

 in spite of the fact that the hereditary substance of both parents 

 is contained in the fertilised ovum, has already been stated in 

 my essay on ' Amphimixis.'' and its solution is to be sought in 

 the struggle of the ids which takes place in every cell in the 

 entire course of ontogeny. This struggle, however, only occurs 

 when the determinants become active, and presumably concerns 

 the biophors which pass into the cell-body, the stronger ones 

 annihilating those with a lesser power of assimilation. It does 

 not concern the determinants which are still • unalterable,' and 

 are inactive as regards the control of the cell. Moreover, the 

 struggle does not occur between the elements of the ' reserve 

 germ-plasm^ which brings about the formation of the germ-cells 

 of the offspring ; and we can therefore understand that the off- 

 spring does not by any means only produce germ-cells con- 



