174 THE GERM-PLASM 



by the cell-divisions which result in the apical cell producing a 

 new shoot. The same is true as regards the formation of a new 

 polype from a blastogenic cell and from an ovum. In both 

 cases the final result is the same, or at any rate very similar, 

 though the method by which it is attained is different. Although 

 a precisely similar organism might be produced by either of 

 the two methods of development, and the primary cells would 

 therefore contain the same determinants in both cases, the 

 grouping of the latter in the two idioplasms at any rate must 

 be different, for they must pass through different groups during 

 ontogeny before their ultimate disintegration into single deter- 

 minants. Even in this very simple case it is necessary to dis- 

 tinguish the 'germ-plasm proper' of the egg- and sperm-cells 

 from the 'apical-plasm' or 'blastogenic germ-plasm.' It is 

 convenient, however, to speak of every kind of idioplasm which 

 contains all the determinants of the species as germ-plasm i?t 

 the wider sense, and to distinguish its various subdivisions as 

 ' blastogenic ' and ' sporogenic ' germ-plasm, and so on ; these 

 latter may all be included under the term accessory germ-plasms 

 or para-ger7n-piasjtis, in contrast to the priiiiary or ancestral 

 germ-plasm. 



Wherever two kinds of germ-plasm occur in the life-cycle of 

 a species, we might be inclined to assume that they change into 

 one another in the course of life. But this view is untenable, as 

 has been shown above, and we are on the contrary forced to 

 assume that both kinds of gerin-piasm continually pass simul- 

 tajieously along the gemt-tracks, aiid that each of thein becotnes 

 active in turn. 



This assumption is unavoidable, for the phyletic development 

 of the species shows that the individual generations in cases of 

 alternation of generations can vary independently and heredi- 

 tarily. It, however, presupposes that special determinants are 

 present in the germ-plasm in each generation, for otherwise both 

 generations would be affected at the same time bv a variation 

 in the germ. A similar assumption must be made in the case of 

 metamorphosis. The wings of a butterfly must be represented 

 in the germ-plasm by a group of determinants. If the wings 

 were formed by the transformation of some of the determinants 

 of the caterpillar, they could never vary without at the same 

 time producing a variation in some parts of the caterpillar, and 

 vice versd. 



