48 PHYSIOLOGY CHAP. 



mental fact ; and the new biometric methods have led to the 

 discovery of facts and laws of capital importance which throw 

 fresh light on the problem of the origin of species, showing it to 

 be far more complex and difficult than had been supposed. 



These laws demonstrate the necessity of carefully distinguishing 

 between variation and variation. 



Some variations are merely quantitative and fluctuating, and 

 when studied by the statistical method are found to be subject to 

 the so-called Law of Quetelet. Such variations are in strict 

 relation with the nutritive conditions, or with the environmental 

 conditions in general, and when these change, the values of the 

 said variations change also, since they are not in themselves 

 hereditary ; but the individuals that exhibit them return to the 

 normal type whenever the conditions of the environment again 

 become normal. It is clear that such variations can have no 

 importance in determining a transmutation of species. 



Other variations, on the contrary, are qualitative and non- 

 nuctuating, and are not subject to the Law of Quetelet. They are 

 fixed, independent of the condition of the environment, and should 

 in reality be termed not variations, but typical hereditary forms, 

 or again elementary species (or races). Each of the classical 

 Linnaean species comprises a greater T)r less number of such ele- 

 mentary species, which in the first instance were confused with 

 the fundamental typical species, and were erroneously held to 

 be simple variations of the same. The majority of our plants 

 and domestic animals are examples of these elementary species. 

 Selection, as practised artificially by man, or effected by Nature 

 in the struggle for existence, is of great importance in the sifting 

 of such elementary species as are more suited to the needs 

 of man, or better adapted to the environmental conditions. It 

 would, however, be a great mistake to think that these elementary 

 species were created and formed by means of selection. In reality 

 selection did nothing more than seal and set in evidence what 

 already existed in a mixed and confused state in the fundamental 

 species, and it created nothing new. Hence the majority of the 

 examples cited by Darwin from .plants and domestic animals are 

 of no value as evidence of the agency of selection in the formation 

 of new species. It is on this account that many speak to-day of 

 a crisis in Darwinism, when this means the theory of selection 

 in a restricted sense, and is not a synonym of evolution. 



The falling-off in the supporters of Darwinism (in this limited 

 sense) has reinforced the adherents of Lamarckism, who attribute 

 the origin of species directly to the environment, to the action 

 of external causes, climate, soil, nutrition, etc. According to 

 Lamarck's original idea (1809), it is the want that creates the 

 organ, which then becomes gradually perfected by use, while with 

 disuse the organ atrophies and disappears. This idea presupposes 



