THE GERM-PLASM 43 



the differences in the biophors composing it ; an animal cell 

 containing, for example, transversely striped muscular substance, 

 or delicate nervous or glandular structures, or again, a vegetable 

 cell enclosing chlorophyll bodies, must contain several different 

 kinds of biophors of which these various cell-structures are com- 

 posed, and which constitute the germ-plasm of a species. 



There must be a great number of different kinds of biophors, 

 for otherwise they could not give rise to so great a variety of 

 cells as exists in the organic world. Nor is it difificult to infer 

 the possibility of an almost unlimited number of different kinds 

 of biophors from their assumed composition. 



As the biophors are not individual molecules, but groups of 

 molecules, nothing prevents us from tracing a large number of 

 variations in them to the widely varying nu7nber of their inole- 

 ailes. But even the che??iical constitution of the molecules is not 

 by any means necessarily the same in all cases, although the 

 possible fluctuations are certainly confined within certain limits. 



Numerous facts show that at any rate in the two main divis- 

 ions of the organic world, the animal and vegetable kingdoms, 

 several of the molecules composing the biophors differ chemi- 

 cally from one another, so that substitutions occur. Whereas 

 glycogen is a constituent which is never absent from animal 

 protoplasm, provided that the latter possesses amoeboid move- 

 ment, this carbohydrate has not yet been discovered in plants, 

 in which, as Hoppe-Seyler suspects, it is probably replaced by 

 amylum, dextrine, or gum. Similarly, the crystalline proteids 

 in plants, which are known as aleurone grains, are chemically 

 different from the yolk-granules in animals. 



A difference in the biophors can, moreover, be conceived 

 without a change in their atomic composition, by regarding as 

 possible a rearrangement of the atoms in the individual mole- 

 cules. The molecule of albumen in particular has, according to 

 the conclusions of modern chemistry, a molecular weight of at 

 least 1,000, so that innumerable isomeric molecules of albumen 

 seem to be conceivable. It is, however, impossible to state how 

 many of them actually exist. 



In order to give as complete an explanation as possible of the 



phenomena of heredity with the aid of the biophors, the latter 



•must be invested with the capacity for a further change, namely, 



a rearrangement of the molecules^ analogous to the isomeric 



rearrangement of the atoms in a single molecule. This assump- 



