THE MUTATION THEORY AND MUTATIONS. 161 



Division neither added nor transferred anything, but left each moiety with all its 

 parts intact. 



Assimilation is the biochemical mill by which like material with like constitu- 

 tion and like organization is generated. The power of assimilation is never "trans- 

 ferred," for it always retains its seat while extending it. As in the growth of a 

 crystal likeness is the necessary result of the apposition of like particles under like 

 conditions, so in the intussusceptive growth of a cell likeness is not received or 

 imparted, but is the necessary product of self-regulating metabolism. 



This is all commonplace, but not entirely out of place whenever confronted with 

 the assumption that heritable qualities are stored in special reservoirs, from which 

 they have to be transported each at its appointed time and to its appointed place, 

 through the help of a complex distributing apparatus. 



The hypothesis of transportation with predetermined distribution is not made 

 any less objectionable by reducing the number of the conjectured pangens. It is 

 no less difficult to guide one pangen and its progeny to precisely the right destina- 

 tions in each generation than to guide two, three, or many. It would be the same 

 inscrutable miracle every time repeated. Hence, de Vries gains no real advantage 

 for his theory when he contends that "a relatively small number of such hypotheti- 

 cal pangens suffices to explain all specific characters, if we allow for the various 

 possible combinations." 4 



These "combinations" of the units have to be maintained in transportation, 

 from stage to stage of development. Says de Vries: 



The pangens must stand in such correlation in the larger or smaller groups 5 that the 

 units of a group, as a rule, will enter into activity at the same time. 



Thus the theory involves not only the difficulty of guiding single pangens, but 

 whole constellations of them. 



Darwin closed his chapter on pangenesis with these words: 



Each living creature must be looked at as a microcosm — a little universe, formed of a 

 host of self-propagating organisms, inconceivably minute and as numerous as the stars of 

 heaven. 



De Vries finds in this an appropriate epigraph for the title-page of his Intra- 

 cellular Pangenesis. A more fitting selection could not have been made with which 

 to announce the parentage of the newborn faith in pangenesis. With the substitu- 

 tion of the single-word "germ-cell" for "creature," the manifold miracle of Darwin's 

 pangenesis is transmuted into that of the cellular pangen-firmament of de Vries. 



In either form of the theory, the visible characters of the species, the origin, 

 relation, variability, heredity, behavior, and control of which constitute the problem 

 of science, are referred to antecedents that vanish in an infinitude of hypothetical 

 entities. These ultimate living units are sometimes singly disposed, sometimes 

 clustered into definite constellations, but in all cases they are held to be separable 

 units, each capable of independent growth, variation, transmission, and precise dis- 

 tribution through the aid of a dividing apparatus evolved for this all-important 

 function. 



4 Intracellular Pangenesis, page 67. 'Synonymous with Darwin's "compound gemmules." 



