CONFORMITY TO TYPE 235 



stance here likewise consists of several equivalent groups of 

 biophors, constituting, 'nuclear rods' or 'idants,' each of which 

 contains all the kinds of biophors of the organism, though they 

 deviate slightly from one another in their composition as they 

 correspond to individual variations. Half the idants of two 

 individuals become united in the process of amphimixis and thus a 

 fresh intermixture of individual characters results. 



"The apparatus for transmission in those multicellular organ- 

 isms in which the cells have undergone a division of labor is essen- 

 tially similar to that seen in unicellular beings; although in 

 correspondence with the greater complexity of their structure it is 

 more complicated. 



"As the process of amphimixis occurs in them also, and the fission 

 of the highly differentiated multicellular individuals seems to be 

 only possible by a temporary return to the unicellular condition, 

 we find that the so-called 'sexual reproduction/ which is of 

 general occurrence among them, consists in all the primary con- 

 stituents (Anlagen) of the entire organism being collected together 

 in the nucleus matter of a single reproductive cell. 



"Two kinds of such cells, which are differently equipped and 

 mutually attract one another, then unite in the process of amphi- 

 mixis and constitute what we are accustomed to call the 'fertilized 

 egg cell/ which contains the combined hereditary substance of 

 two individuals. According to our view, this hereditary substance 

 of the multicellular organisms consists of three orders of vital 

 units, the lowest of which is constituted by the biophors. In the 

 unicellular forms a more or less polymorphic mass of biophors 

 having a definite arrangement, constitutes the individual nuclear 

 rods or idants (chromosomes), several of these making up the 

 hereditary substance of the nucleus which controls the cells; and 

 similarly in these higher forms, groups of biophors, arranged in a 

 certain order, constituting the primary constituents of the in- 

 dividual cells of the body, and together form the second order of 

 vital units the determinants. The histological character of every 

 cell in a multicellular organism, including its rate and mode of 

 division, is controlled by such a determinant. The germ cell, 

 however, does not contain a special determinant for every cell 

 unless it is to remain independently variable. The germ cell of a 

 species must contain as many determinants as the organism has cells 

 or groups of cells which are independently variable from the germ 

 onwards, and these determinants must have a definite mutual 

 arrangement in the germ plasm, and must therefore constitute a 

 definitely limited aggregate, or higher vital unit, the 'id.' From 

 the facts of sexual reproduction and heredity we must conclude 

 that the germ plasm contains many ids, and not a single one only. 

 The formation of hybrids proves that the two parents together 

 transmit all their specific characters, so that in the process of 

 fertilization each contributes a hereditary substance which con- 

 tains the primary constituents of all parts of the organism that is, 

 all the determinants required for building up the new individual. 

 The hereditary substance becomes halved at the final stage of 

 development of the germ cells, and consequently all the deter- 



