14 SCIENCE PROGRESS. 
which it is desirable to perpetuate. These are kept for 
the propagation of the stock, and a repeated attention is 
paid to the same circumstances, till, the effect continually 
increasing, a particular figure, colour, proportion of limbs, 
or any other attainable quality, is established in the race, 
and the uniformity of the breed is afterwards maintained by 
removing from it any new variety which may casually spring 
up in it.” 
The main result of Darwin’s indefatigable labours on 
the formation of domestic races could not be more ac- 
curately summarised than in these words published in 1826. 
Prichard expresses himself as uncertain whether do- 
mestic animals are more prone to vary than others, but 
considers that the artificial conditions may in all prob- 
ability ‘‘occasion deviations in their progeny”. 
The influence of climate seemed to him the most im- 
portant of all causes of race-formation—so important in fact 
that he discusses its examples under a separate section, while 
the adaptation of races, animal and human, to their climates 
form the subjects of the concluding sections vi. and vit. 
The examples of the effect of climate are brought 
forward in section v. (p. 558), entitled, ‘Instances of 
Variety in the Breed, Arising from the Operation of Exter- 
nal, Chiefly of Local Causes”. The first instance is that of 
the swine of Cuba which are said to be twice the size of the 
parent breed. He then instances the peculiar and uniform 
colour of the cattle and horses ‘‘ descended from the 
variegated domestic breeds” which have become wild in 
South America, and the common bear which differs in 
colour in various European localities. 
When the races of several distinct species resemble 
each other in a single locality it is fairly maintained that 
some special local influence may be strongly inferred. 
Thus it is stated that the Angora breeds of rabbits, goats, 
and cats are remarkable for their long fine silky hair and 
white colour. ‘‘ These characters . . . indicate a common 
cause, which must be some peculiarity in the circumstances 
under which these animals exist in the climate and situa- 
tion occupied by them.” 
