RAY LANKESTER 11 



Here then we see the two foremost British biologists of our 

 day, the one in doubt whether change in environment can be 

 a direct cause of modification, and, filled with these doubts, 

 willing to accept as a postulate that positive features cannot 

 be added to the original stock, whereby he is led to an utterly 

 perverse hypothesis ; the other equally denying that there can 

 be external influences of such a nature that specific variation — 

 i.e. variation in particular directions — may be induced, and 

 taking the stand that variation is multitudinous, the favourable 

 variation alone having the opportunity to be propagated and 

 reproduced. 



Now if there be one fact that is constantly being impressed 

 upon the student of immunity and the worker in pathogenic 

 bacteriology, it is that " direct adaptation " (i.e. specific modifica- 

 tion in response to a specific alteration in environment within 

 limits which will presently be laid down) is one of the basal 

 phenomena of living matter. Our studies make it impossible 

 for us to be blind to the fact that environment is capable of 

 exerting a profound influence upon living beings, bringing about 

 modifications of function and even of structure in particular 

 directions. But evidently our experience and the diverse obser- 

 vations upon which that experience is based are unknown to the 

 academic biologists, although some biologists are beginning to see 

 light. Thus it delighted me to run across the following admission 

 in a valuable work published within the last few weeks — Pro- 

 fessor D'Arcy Thompson's Growth and Form : 1 "So long and 

 ' so far as ' fortuitous variations ' and the ' survival of the fittest ' 

 remain engraved as fundamental and satisfactory hypotheses 

 in the philosophy of biology, so long will these ' satisfactory 

 and specious ' causes tend to stay ' severe and diligent enquiry ' 

 to the great arrest and prejudice of future discovery." With 

 this strong opposition on the one hand, and encouragement on 

 the other, it has seemed to me a useful task to bring together 

 and marshal in order the data bearing upon these matters as 

 they present themselves to us, workers in medical science. 



1 Growth and Form, by D'Arcy W. Thompson, F.R.S., Camb. Univ. Press, 

 1917, p. 6. 



