452 THE GERM-PLASM 



substance 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 labour, is 

 essentially 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 fusion of highly-differentiated multicellular 

 individuals seems only to be possible by a temporary return to 

 the unicellular condition, we find that the so-called ' sexual 

 reproduction,"' which is of general occurrence amongst them, 

 consists in all the primary constituents (' Anlagen') of the entire 

 organism being collected together in the nuclear 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 amphimixis, and constitute what we are 

 accustomed to call the 'fertilised egg-cell," which contains the 

 combined hereditary substances of two individuals. 



According to our view, this hereditary substance of the multi- 

 cellular organisms consists of three orders of vital units, the 

 lowest of which is constituted by the biophors. In the uni- 

 cellular forms a more or less polymorphic mass of biophors, 

 having a definite arrangement, constitutes the individual nuclear 

 rods or idants, several of these making up the hereditary sub- 

 stance of the nucleus which controls the cells ; and similarly 

 in these higher forms, groups of biopliors. arranged in a certain 

 order, constitute the primary constituents of the individual cells 

 of the body, and together form the second order of vital units, — 

 the cell-determinants, — or simply, the ^ deterviniafits.'' 



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-plasm does not, however, 

 contain a special determinant for every cell ; but cells of a simi- 

 lar kind, when, like the blood-cells, they are not localised, may 

 be represented by a single determinant in the germ-plasm. On 

 the other hand, every cell, or group of cells, which is to remain 



