i8o THE MUTATION THEORY 



favourable discontinuous variations in wild nature is due solely to 

 difficulties of observation. But there are no such difficulties in 

 observing the neglected human species which we are so very capable 

 of observing. It is not really beneath the dignity of science to utilize 

 familiar facts. Mankind has spread over the whole habitable 

 globe ; it inhabits very diverse environments ; it is numbered in 

 millions, and has hundreds, if not thousands of stable varieties. 

 Some races such as the Esquimaux and the Tierra-del-Fuegians, 

 are apparently as ' pure ' as natural races of lower animals ; others 

 are simple mongrels ; yet others are compound mongrels. 

 Some mongrel human races are very ancient ; others are com- 

 paratively new. 1 Racial changes of a permanent sort there have 



The mutants, which were of at least seven different types, were comparatively 

 few in number in the field. Most of the types were weakly and perished. In the 

 field two types " have held their own during the last sixteen years, and probably 

 more, without, however, being able to increase their numbers to any noticeable 

 extent. Others perish as soon as they make their appearance, or a few individuals 

 are allowed to bloom, and probably leave no progeny. But perhaps the cir- 

 cumstances may change, or the whole strain may be dispersed and spread to new 

 localities with different conditions. Some of the latter may be found favourable 

 to the robust gigas or rubrinervis, which requires a dryer air, with rainfall in the 

 spring-time and sunshine during summer " (Species and Varieties, p. 574). Muta- 

 tions are comparatively few, changes of climate rare, and the dispersal of most 

 plants, except by human agency, slow. The chance of these mutations surviving 

 in nature seems, therefore, somewhat remote. It is significant that de Vries 

 " made experiments with some hundred species that grow wild in Holland. . . . 

 No real mutability could be discovered " (p. 520) in the native plants growing 

 in their ancestral environment. Or, to express the fact in other and probably 

 more correct terms, these natural varieties revealed no latent characters. To 

 account for the fact that O. lamarckiana mutated frequently while the native 

 Dutch plants mutated not at all, the hypothesis was formulated that in the life- 

 histories of species periods of great mutability alternate with periods of stability. 

 " Of course this mutable state must have had a beginning, as it must sometimes 

 come to an end. It is to be considered as a period within the lifetime of the 

 species, and probably it is only a small part of it " (p. 29). Manifestly this de- 

 duction, like that of colour-factors, is a pure guess, invented to bolster up another 

 hypothesis which was found not to agree with reality. We may predict 

 with entire confidence that every variety which has evolved under artificial 

 selection and has been frequently crossed is an ' eversporting variety,' whereas 

 every species which has evolved under Natural Selection is stable. 



1 " In the case of a problem like that of man, complicated as it is by the fact 

 that he has ' crossed more often than any other animal,' and further rendered 

 intractable by the circumstance that he is not amenable to experiment, a great 

 difficulty arises in discovering which are the actual allelomorphs concerned " 

 (Mr R. H. Lock, Nature, i/th Oct. 1907). " How can the fact that human races 

 have crossed more often than any other animal complicate the problem ? My 

 statement implied, not that every race is a chaotic mixture of types, nor even that 

 there are no pure types, but only that we have here a very large and varied mass 

 of material on which to found our judgments " (G. Archdall Reid, Nature, Oct. 

 3ist 1907). 



