Vitality (ind Organization of Pruloplasm. 21 



Although it is a fact that the germ-plasm evolves all tlie diverse 

 tissues of the adult organism, it remains yet to be discovered how it has 

 acquired its diiferentiated efficiencies, and how it manages atUially to 

 realize' the same -during ontogenetic evolution. It was principally to 

 "answer these questions that Weismann formulated his theory. Taking 

 the chromosomes of the nuclear plasm to be exclusively germ-plasm, 

 he necssarily conceived their structure to be of a highly complex nature. 

 For how otherwise could they evolve the diverse structures of the adult ^ 

 organism with all their specifically differentiated characteristics. The 

 chromosomes must then contain special germinal representations for all 

 the different specializations found in adult organism, and these repre- 

 sentatives must occupy definite positions, and must be definitely grouped, 

 in order systematically and in due sequence to evolve the differentiated 

 structures. Each independently varying and inheritable trait of adult 

 organisms, "even a mole on the skin, or a colored spot on the wing of a / 



a butterfly," Weismann believes, to be representatively pe4-formed in the /'"'''y/ 

 germ-plasm by specialized component units of the same. These spe- / 



cializcd formative units he calls " determinants. " because they are held ' 



respectively to determine the variform characteristics of the evolving 

 structures of the adult organism. 



In the chrohiosomes the determinants are conceived to be specifically 

 grouped so as to form complete assortments, representing every kind of 

 structural differentiation destined to appear in the adult organism. 

 Such complete assortments of determinants, definitely arranged within 

 the chromosomes, Weismann names an 'JtcL^ And to explain certain 

 biological phenomena he believes the chromosomes to be composed of 

 a number of such ids, constituting what he names an "idant ." The 

 determinants themselves are held to be composed of a definite group 

 of ultimate vital units, which Weismann calls '^biophorcs." These 

 biophores or lifebearers are, like the gemmules of Darwin and the pan- 

 genes of De Yries assumed to multiply by means of self-division. And 

 Weismann not only allows his biophores or ultimate vital units, to mul- 

 tiply by self-division, but makes his determinants, in which the biophores 

 are specifically grouped, likewise multiply by self-division as a whole. 

 And in the same manner his ids, in which determinants in full assort- 

 ment are specifically grouped. And finally also his idants, in which 

 a number of ids are held to be contained. Thus all different members 

 of his hierarchy of differently grouped biophores are assumed to be en- 

 dowed with the same vital property as the biophores themselves. JThey 

 propagate their kind, and must possess, consequently, all vital efficien- 

 cies inYQlved in reproductiop. 



It is obvious that under this theory the phylogenetic problem has to 

 consist in showing how the biophores as original life-bearers come to be 

 specifically differentiated, and speci&anv_group,ed, so as to form the 

 vast supply of divers determinants required ; and how these determinants 

 themselves come to be specifically grouped so as to form ids, and the ids 

 again grouped so as to form idants. Xow the question is, have we any 



