76 'DETERMINANTS' VERSUS 



made up of aggregates of granules — the granules in each case 

 being what Weismann calls 'ids,'' The number of 'chromo- 

 somes' varies much in different kinds of animals and plants 

 though it " remains the same in every cell-generation throughout 

 development, as it is the same in all the individuals of a species." 

 Thus, according to Weismann, " in some worms there are only two 

 or four ; in the grasshopper there are twelve ; in the mouse, the 

 trout, and the lily there are twenty-four ; in snails thirty-two," 

 while in Man "the chromosomes are so small that their normal 

 number is not certain — sixteen have been counted" {loc. cit. I, 

 p. 291). 



After these well-established facts we come into the region 

 of pure hypothesis. The minute granular 'ids' are assumed to 

 be composed of a vast number of altogether hypothetical units 

 to which Weismann gives the name of 'determinants,' though 

 he also speaks of them as 'primary constituents.' Each 'id,' of 

 which there are usually very many in each chromosome, is 

 represented to be a " complex of primary constituents necessary 

 to the production of a complete individual," or, as he says a little 

 further on, "as composed of a mass of different kinds of parts 

 each of which bears a relation to a particular part of the perfect 

 animal, and so to some extent represents its ' primary constituents' 

 (Anlagen), although there may be no resemblance between these 

 'primary constituents' and the finished parts." There must, he 

 says, be as many of these 'primary constituents ' or 'determinants' 

 " as there are regions in the fully formed organism capable of 

 independent and transmissible variation, including all the stages 

 of development," — even where these latter are so very different as 

 they are found to be in many Crustacea and in insects. 



Thus, according to these hypotheses of Weismann, each granule 

 of one of the minute chromosomes existing in a nucleus (that is 

 each ' id ') must contain all the infinitely numerous entities, known 

 as 'determinants,' which are assumed to be necessary for the 

 development, let us say, in a butterfly, of the larva, the pupa, 

 and the imago ; and in the latter for the myriads of every minute 

 part or scale of the butterfly's wing ; since, as he says, "the 

 primitive cell of the butterfly's wing must contain all the determi- 

 nants for the building up of this complicated part." Divisions 

 of the cells will continue, he adds, " until the determinant archi- 



■ This abstract of liis views is gathered from Lects. XVII,, XVIII., and XIX. 

 on " The Germ-Plasm Theory," pp. 345-416. 



