MONSTEOSITIES. 229 



cause of these individual differences, though in detail usually 

 utterly unknown to us, depends partly or entirely on certain 

 influences which the organs of propagation in the parental 

 organism have undergone. 



A second law of indirect adaptation, which we shall 

 call the law of ^monstrous or sudden adaptation, is of less 

 importance and less general than the law of individual 

 adaptation. Here the divergences of the child-organism 

 from the parental form are so striking that, as a rule, we 

 may designate them as monstrosities. In many cases they 

 are produced, as has been proved by experiments, by the 

 parental organism having been subject to a certain treat- 

 ment, and placed under peculiar conditions of nutrition ; for 

 example, when air and light are withdrawn from it, or when 

 other influences powerfully acting upon its nutrition are 

 changed in a certain way. The new condition of existcDce 

 causes a strong and striking modification of form, not 

 directly of the organism itself, but only of that of its de- 

 scendants. The mode of this influence in detail we cannot 

 discover, and we can only in a very general way detect a 

 causal connection between the abnormal formation of the 

 child and a certain change in the conditions of existence 

 of its parents exerting a special influence upon the organs 

 of propagation in the latter. The previously mentioned 

 phenomenon of albinism probably belongs to this group of 

 abnormal or sudden variations, also the individual cases 

 of human beings with six fingers and toes, the case of 

 the hornless cattle, as well as those of sheep and goats 

 with four or six horns. The abnormal deviation in all 

 these cases probably owes its origin to a cause which 

 at first only affected the reproductive system of the 



