INHERITANCE OF ACQUIRED CHARACTERS 181 



" (This case was related to me in full detail by the father with 

 the deformed finger, and with whom I was personally acquainted. 

 He was an eminent physician, the president of a large and 

 reputable medical college, and his name is well known to the 

 profession.) " 1 



It seems only reasonable, then, to admit that suddenly 

 acquired somatogenic characters are occasionally, though probably 

 very rarely, transmitted by heredity in a sufficiently pronounced 

 form to be recognizable, but even if this were not so we should 

 not be justified in concluding that all the characters which an 

 organism exhibits have their origin in the first instance in modi- 

 fications of the germ plasm. It must be remembered that a great 

 many somatogenic modifications are the result of what we may 

 call the normal action of the environment, and that such action 

 may extend over very long periods of time, in which many 

 thousands of generations may be produced. In such cases the 

 stimulus, whatever it may be, to which the organism responds by 

 modification in bodily structure, is repeated a vast number of 

 times, and therefore seems much more likely to produce an 

 inheritable effect than a single accidental or experimental injury. 

 A single drop of water falling on a stone makes no visible 

 impression, but if the dropping goes on for a long time the stone 

 will gradually be worn away, and it is by no means essential to a 

 belief in the heritability of acquired characters that such 

 characters should be immediately inherited in full perfection. 

 It may be merely a question of time. 



It is a well known fact that the "habit" and even the 

 structure of a plant are largely determined by the conditions 

 under which its growth takes place. 2 A plant growing in a hot- 

 house may acquire a very different habit from another of the 

 same species growing in the open air. Many alpine or sub-alpine 

 plants have become adapted to their peculiar environment by 

 various highly characteristic modifications, amongst which a 

 reduction in the size of the leaves is one of the most conspicuous, 

 and such plants may be induced to change their mode of growth 

 by simply removing them to sufficiently warm and sheltered 

 situations, in which their habit comes to approach that of their 

 lowland relatives. In such cases it is difficult to say how far 



1 This is another of the striking cases collected by Professor Brewer and quoted 

 in Cope's " Primary Factors of Organic Evolution," pp. 433-4. 



2 The reader should consult the quotations from Lamarck bearing upon this point 

 given in Chapter XXIV., especially the case of Ranunculus aquatilis. 



