EwART — Variation : Germinal and Environmental. 359 



from the most docile and most fertile members of their flocks and herds, 

 the tamest and least nervous of their rabbits, pigeons, &c., and the fleetest 

 or keenest scented of their hounds, and not because acquired variations are 

 transmitted. 



If definite acquired variations are not transmitted in cultivated i^lants or domestic 

 animals, it is inconceivable tliat they are transmitted in human beings, that the 

 higher branches of the Imman family owe any of their finer traits (aptness to 

 acquire knowledge and the like) to the gradual accumulation during many 

 generations of specific somatic (non-germinal) variations. 



(2). The i}ijltience of nutrition and somatic wellheing on the germ-plasm. 



If it is impossible to endow the offspring with special somatic characters or 

 traits acquired in virtue of a heritage of individual plasticity, let us see whether 

 there is any evidence that the germ-cells more or less accurately reflect the 

 condition or general fitness of tlie individual in which they are formed, as buds 

 bear an intimate relation to the plant on which they grow. Though there is no 

 evidence that the blacksmith can endow his children with a strong riglit arm, there 

 may be good reasons for believing that the germ-plasm of a mature, vigorous, 

 healthy individual, is likely, other things being equal {e.g. the prepotency), to 

 overcome, during the conjugation of the germ-cells, the germ-plasm of a less 

 matured and less mentally and pliysically fit individual. If it can be shown that 

 the germ-plasm not only in a way reflects the vigour or general fitness of the 

 somatic tissues, but also that the condition {e.g. ripeness) of the germ-plasm to a 

 certain extent determines the nature of the combinations formed during conjuga- 

 tion, and also whether the male or female parent will control the development, it 

 will be evident that the environment is indirectly an important factor in causing 

 variation, without which progressive development is impossible. 



I find some horses, colts as well as fillies, mature sooner than others ; that most 

 horses reach maturity sooner than zebra-horse hybrids, and that hybrids mature 

 sooner than zebras. Again I find that the cross-bred offspring of pigeons obtained 

 in the early spring differ in various ways from birds bred during summer. In the 

 case of fillies, the ones kept indoors and well fed during the winter reach maturity 

 sooner than the fillies infested with the parasite strongylus, or allowed to run out all 

 winter. Further, while there are often signs of ovulation in stall-fed mares all 

 through the year, mares only receiving hay, and the occasional shelter of a shed 

 during winter, may only begin to show signs of ovulation in April or May. Again, 

 animals in too good a condition, like animals out of condition, owing, e.g., to a 

 change of habitat, are often, at least for a time, sterile. 



