NATURE AND CAUSE OE VARIATION. 303 



of color centers of metameric origin and arrangement. This ancestral endow- 

 ment, which represents simply the repetition for an immense number of gener- 

 ations of the same series of stages, is used, as I have shown by all the species 

 in the genus, as the background of antecedent stages, upon which are further 

 worked out, as each group and species by its specific nature dictates, its type 

 of coloration. The same fact is true of the other systems of organs. The 

 question at issue is not so much the sequence of stages, because that all 

 will admit, but how we are to interpret this? We know that development 

 is a complicated, orderly, constant phenomenon, and the real question is 

 whether this orderly development is conditioned and controlled by material 

 units preexisting in the germ plasm, each endowed with all the attributes and 

 potentialities of the parent organisms, or whether it is due to the conditioning 

 of any given stage by the preceding stages. In other words, are we to con- 

 ceive of the germ plasm as a composite aggregation of an immense number of 

 individually endowed vital units, each in reality a unit organism, and this 

 complex society creating the individual (soma) for its use and habitation, 

 or shall we conceive of the germ plasm as an entity, as protoplasm differing 

 from other organic matter only in its conservative and generalized nature? 

 Unfortunately we can not decide this question in positive terms in the present 

 state of our knowledge. 



Biologists seem to be nearly all of the opinion that the germ plasm is prob- 

 ably contained within the nucleus, and is largely, if not entirely, represented 

 by the chromatin of the nucleus. From this chromatin come, according to 

 recent researches, a considerable part of the cytoplasmic contents of the germ 

 cells ; also from the nuclei by chromatolysis are derived the internal secretions, 

 enzymes, cytolyzines, cellular toxins, etc., whose action directly controls and 

 conditions growth and nutrition. Even such characters as color are directly 

 initiated and controlled by the production of materials elaborated from the 

 chromatin of the nucleus, which react upon one another to produce, as in 

 these beetles, chitin and oxy-azo pigments. From the investigations in physio- 

 logical chemistry it is rapidly becoming more and more certain that all organic 

 products of the body are directly or indirectly the product of the chemical 

 activity of the nuclear material. At the present time there are known a great 

 variety of purely chemical processes and products originating from the chro- 

 matin, and upon the basis of the predetermination hypothesis they must be 

 predetermined also, and there must therefore exist within the germ plasm an 

 immense number of units, say "biophores" or "pangenes," to be later localized 

 in particular cells and to control the multifarious chemical processes due to 

 chromatic activity. These ultimate units, according to Weismann, "all pos- 

 sess the fundamental characters of life, dissimilation, assimilation, growth, 

 and multiplication by division. We must also ascribe to these in some degree 

 the power of movement and sensibility" (p. 369). Now, this is all very 

 22 T 



