Weismann’s Explanation of Coordinated Variations 215 
every fortuitous variation that is possible, both plus and 
minus, actually develops, the net result after the elimi- 
nation of the minus variations must be that the muscles 
would be stronger. But this initial increase, this first 
impulse toward strengthening, would be in turn the 
cause of a phylogenetic tendency to a further strengthen- 
ing, because it would indicate that these muscles were 
represented in the germ plasm by determinants which 
are endowed with a greater power of growth, and con- 
sequently with greater power of assimilation. “The 
affluence of nutritive fluids would become proportionally 
augmented and would contribute likewise to giving the 
plus variations a preponderance over minus variations. 
There would thus be a phylogenetic tendency toward the 
continual increase of these muscles and it would endure 
just as long as the increase in the weight of the head, 
and would stop when the latter stopped. For in this 
case the plus variations of the determinants would be 
eliminated by individual selection, as soon as_ they 
attained selectable value.” *** 
But this artificially constructed hypothesis, which did 
not hold good at all in the case of rudimentary organs, 
is still less adapted to the case of co-ordinated varia- 
tions. For in these phenomena it appears still more 
clearly that in phylogenetic changes there are concerned 
not simply exclusively plus or minus variations, but 
transformations which might be constituted by a com- 
bination of increases in one direction and decreases in 
another, or might not be susceptible of being decomposed 
into merely quantitative variations. It should be noted 
further that for certain correlative, histological varia- 
168\Weismann: Neue Gedanken zur Vererbungsfrage. P. 22. 
