24 THE PRINCIPLES OF HEREDITY 



of acquirements is causing evolution through inherited 

 benefits (plentiful food, etc.), cessation of Natural Selection 

 is resulting in degeneration. We saw that the only 

 instances in which the two doctrines are seemingly com- 

 patible are when (as in the cases of antelopes hunted by 

 carnivora) Natural Selection causes elimination of the unfit 

 by violent death, while at the same time transmission of 

 acquirements is causing evolution among the survivors by 

 the inherited effects of use. But, as a matter of fact we are 

 in possession of conclusive evidence that the effects of use 

 (and presumably also of disease) are never transmitted. We 

 shall deal with that evidence presently. Meanwhile it follows 

 that Natural Selection and the transmission of acquirements, 

 if they both exist in nature, are, not only sometimes, but 

 always at war. They invariably act in opposition. Must we, 

 then, conclude that Natural Selection has called into exist- 

 ence a power which tends to stultify its own operations ? 



40. As long as we think of inheritance among multi- 

 cellular creatures in terms of the whole organism, just so long 

 does the transmission of acquirements seem natural and 

 probable. Thus, if we think vaguely, as we are apt to do, 

 that a man's head is derived from his parent's head, his 

 limbs from his parent's limbs, his lungs from his parent's 

 lungs, we see nothing incredible in the belief that changes 

 occurring in the parent tend to be reproduced in the child. 

 But the moment we descend to accurate details and think 

 in terms of the germ-cell, immediately we see that the 

 transmission, if it occurs, is very wonderful. We are then 

 forced to ask ourselves how this amazing power arose. 

 Natural Selection could not have evolved a power which 

 renders its own operations nugatory. How then did it arise ? 

 The only alternative is an appeal to miracle. 



41. What is the machinery by which it works ? By what 

 means do different acquirements so affect the germ-plasm, so 

 change it, as to cause their own reproduction in the offspring ? 

 It has been maintained that the multicellular body is not 

 really multicellular, but in a true sense unicellular. The separ- 

 ation between the various fixed cells of the organism is 

 said to be incomplete ; they are connected by protoplasmic 

 bridges. But, even supposing we agree to regard the multi- 

 cellular body, not as a community of adherent cells, but as a 

 sort of gigantic unicellular organism, our difficulties do not 

 diminish. It still remains true that the offspring is derived 

 from a minute fraction of this body, and it is just as hard to 

 believe that the fraction is influenced in millions of precise 



