182 Mr. P. R. Lowe on [Ibis, 



of, from his forbears, human and otherwise ; and I believe 

 it is as certain that the finely vermiculatcd markings of 

 G. lineatus were derived in like manner from its various 

 progenitors. It is important to dwell upon these points in 

 order to make evident the differences between mutational 

 and environmental subspecies. It seems well-nigh incon- 

 ceivable, even as an abstract proposition, to picture Natural 

 Selection seizing upon a small favourable variation here and 

 another there, in the direction of fine vermicuJations which 

 harmonised with the immediate environment, and finally 

 building them up into the perfect article by the elimination 

 of the unfavourable variations *. Consider for a moment the 

 various types of environment to which Pliasianus colcldcus 

 has been exposed for a thousand years in the British Isles. 



We know that the old English Pheasant was introduced 

 from the banks of the river Phasis in Colchis (hence the 

 name Phasianus colchicus), and very probably by the Romans 

 (c/". Newton's ' Dictionary of Birds '). Are we to believe that 

 the environmental conditions obtaining in southern Russia 

 are so precisely identical with those in the British Isles that 

 in a thousand years or more no perceptible change in colour- 

 pattern would have been brought about ; or was it not more 

 likely that the ^'English Pheasant" remained unchanged, 

 and would have continued to remain unchanged, homozygous 

 as every individual was, until crossed with newly introduced 

 races from still farther east, such as the Ring-neck ? 



" Pure-bred^' as P. colchicus was when introduced by the 

 Romans, I cannot but believe that it would have remained 

 " pure-bred " to the last if it had been left alone, since there 

 is no evidence that there was any innate tendency to variation 

 in its constitution, or any very likely natural facilities for 

 adequately isolating such variations if they arose. 



* Note. — On the contrary, there -would appear to be little doubt that 

 G. lineatus, along with most of the subspecies of the genus Genncens 

 which have been described from Burma and adjacent countries, is 

 a mendelian segregate, and the most likely explanation of its origin 

 would appear to have been a crossing between two such forms as 

 G. horsfieldi and G. nycthemeriis (cf. J. C. Phillips, ' Genetics,' vi. 1921, 

 p. 376). 



