ADAPTATION 191 



chology can propound. Philosophers might perhaps encourage 

 themselves to attack the problem of the nature of memory by 

 reflecting that after all the process may in some of its aspects 

 be comparable with that of inheritance, but the student of gen- 

 etics, as long as he can keep in close touch with a profitable basis 

 of material fact, will scarcely be tempted to look for inspiration 

 in psychical analogies. 



For a summary of the recent evidence I may refer the reader 

 to Semen's paper 1 where he will find a collection of these obser- 

 vations described from the standpoint of a convinced believer. 

 At the outset one cannot help being struck by the fact that of 

 the instances alleged, very few, even if authentic, show the trans- 

 mission of acquired modifications which can in any sense be re- 

 garded as adaptative, and many are examples not so much of a 

 transmission of characters produced in the parents as of variation 

 induced in the offspring as a consequence of treatment to which 

 the parents were submitted, the parents themselves remaining 

 apparently unmodified. No one questions the great importance 

 of evidence of this latter class as touching the problem of the 

 causes of variation, but it is not obvious why it is introduced in 

 support of the thesis that acquired characters are inherited. 



It is most difficult to form a clear judgment of the value of 

 the evidence as a whole. To doubt the validity of testimony 

 put forward by reputable authors is to incur a charge of obstinacy 

 or caprice; nevertheless in matters of this kind, where the alleged 

 phenomena are, if genuine, of such exceptional significance, belief 

 should only be extended to evidence after every possible source 

 of doubt has been excluded. We believe such things when we 

 must, but not before. At the very least we are entitled to require 

 that confirmatory evidence should be forthcoming from inde- 

 pendent witnesses. So far as I have seen, this requirement is 

 satisfied in scarcely any of the examples that have been lately 

 published, and until it is, judgment may reasonably be suspended. 



In some cases, however, the facts are not doubtful. Stand- 

 fuss, by subjecting pupae of Vanessa urticae to cold, produced 



1 Semon, R., Der Stand der Frage nach der Vererbung erworbener Eigenschaften, 

 published in Fortschr. der naturw. Forschung., Bd. n, 1910. 



