1046 LIFE : OUTLINES OF GENERAL BIOLOGY 



and the plants exhibited once more the original Alpine characters. 

 In all probability the environmentally induced modifications had 

 not taken any grip of the germinal constitution. There was no con- 

 vincing evidence of hereditary entailment. In this case, and various 

 kindred ones, the soil was probably the most important factor, but 

 it is impracticable at present to separate the strictly meteorological 

 conditions of climatic changes from the others that may be involved. 



It is important not to think of these matters too simply. Thus, 

 as Goldschmidt points out, the normal development of particular 

 characters, such as general growth and pigment formation, has been 

 "harmonised" for a definite environment. But they have different 

 temperature coefficients, and novel conditions may throw them out 

 of harmony. Moreover, modifications resulting from climatic change 

 must not be thought of as necessarily beneficial. Thus some Lepi- 

 doptera tend to melanism in the cold and others at high tempera- 

 tures, without there being any demonstrable advantage in either 

 case. 



(8) If evidence could be obtained of the hereditary entailment of 

 climatic modifications, this would serve as a basis for a Lamarckian 

 theory of acclimatisation. What Lamarck laid stress on was func- 

 tional modification, but for plants and for "apathetic or insensitive 

 animals" he allowed that there might be importance in modifications 

 directly induced by peculiarities in the environment, without there 

 being any appreciable change of function. This is a distinction not 

 always easy to draw, and in any case while one might call tanning a 

 directly induced environmental modification, there are others which 

 may be at least interpreted as the outcome of functional change in 

 a new climate. It was to this kind of change that Darwin referred 

 when he wrote (1868) : "How much influence ought to be attributed 

 to inherited habit or custom in the acclimatisation of animals and 

 plants is a much more difficult question" — much more difficult than 

 the question of acclimatisation by man's selection of new varieties. 

 Darwin's conclusion was that "habit" did not count for much; but 

 it is necessary to inquire afresh whether there are any facts sup- 

 porting the Lamarckian interpretation. 



Bordage records some observations on peach-trees (Prumis 

 persica) grown from seed of European origin sown in Reunion. 

 For ten years or so the trees shed their leaves, as in Europe. Later 

 on, after twenty years, a considerable degree of evergreenness was 

 exhibited. There was no bare period. A climatic modification was 

 thus eventually brought about. When seeds of these partial ever- 

 greens were sown in the lowlands they grew into trees verdant 

 throughout the year, but the same was true of seeds sown in certain 

 mountainous districts with a considerable degree of frost. They also 

 grew up into young peach-trees which were also evergreen. But 

 European seeds sown in similar situations developed into ordinary 



