1997] FUNDAMENTAL PRINCIPLES OF HEREDITY 313 
of an organ these biophors are distributed between the cells; and 
the proper biophors in each cell constrain it to play its specific part 
in the organism. 
Those cells which constitute the direct line of descent between the 
reproductive cells of one generation and those of another are formed 
by true divisions of the germ-plasm, with all its determinants. But 
we are met by the facts of propagation by fragments composed only 
of tissue-cells in Animal, and still more in Plants, where specialised 
tissue-cells revert to an embryonic condition, or rather beget 
embryonic cells with a complete germ-plasm. To explain this diffi- 
culty, we must suppose that in these cases a portion of complete 
germ-plasm has passed at their formation into such tissue-cells, and 
that it has remained dormant until the stimulus of separation from 
the colonial organism has revived its vitality. Again in the four- 
celled stage of the segmented embryo of various widely distinct 
Animals (even in the sixteen-celled stage of some Medusae) it is 
possible to isolate a single cell, which then develops into a complete 
embryo, though had it remained associated with its fellows it would 
have formed only a definite part of the embryo. Here again we find 
the assumption of the existence of dormant determinants, which be- 
come active only in the separated cell, adduced by Weismann to save 
the theory. This assumption is also used to explain alternation of 
generations, where the Moss-plant and Moss-urn, or the Fern-scale 
and Fern-plant alternate ; their germ-plasm must contain two sets of 
determinants, one for the first, the other for the second generation, 
alternating in sleep and waking like the printer and the hatter in 
Box and Cox. We are reminded of the complex epicycles required 
to render the universe workable on Ptolemy’s geocentric hypothesis, 
and the Spanish king’s comment thereon. “ Had I been consulted 
at the creation, I could have simplified matters.” 
So far indeed, this might be held as a formal or fictive hypo- 
thesis to explain the mechanism of heredity on the basis of Special 
Creation—each organism being created fully equipped with its 
own proper germ-plasm, determinants, biophors, and all. But no; 
Weismann is a firm believer in the theory of common descent, and, 
as we have seen, he and his school profess to be the only true 
Darwinians ; and we come to his Theory of Variations. 
The germ-plasm with its contained determinants, as it lies 
in the reproductive cells of the body, is subject to nutritive 
changes, and consequently to constant slight variations which 
apparently are not correlated with anything else whatever. The 
haphazard variations, of the determinants induce corresponding, and 
1 This essay was written nearly two years ago. Since then Weismann has enlarged 
his theory by the hypothesis of germinal selection. Without going into this we may 
note that it makes no difference to the present argument. 
