1 92 1.] Letters, Extracts, and Notes. 347 



merely quantitative as opposed to qualitative, and it would 

 be interesting in this connection to make a comparative 

 examination of the number of present-day subspecies oc- 

 curring in a genus where the colours are due to peculiarities 

 of structure in the feathers and the reflection of light upon 

 them — as, for example, in many species of Cinnyris or 

 Nectarinia, — and, on the other hand, in a genus where the 

 colour is directly due to pigment which can be acted on 

 by humidity, light, etc. 



Mutational variations, on the other hand, present charac- 

 teristics which are directly derived from the action of factors 

 resident in the germ-plasm, which are totally independent 

 in their origin of the action of environment, and which are 

 stable — o-iveu favourable conditions. jNIutational variations 

 iu all probability never intergrade, and they are dependent 

 on isolation whatever form that isolation may take, either 

 geographical or physiological. Natural selection may here 

 play a decisive part in determining their future. The 

 ignoring by ornithologists of these two different forms of 

 variation has led, in our opinion, to the making of sub- 

 species, which, in fact, have very different values and rank. 



It appears, therefore, that before we can answer the 

 question propourided by Mr. Loomis " Of what scientific 

 value is a subspecies?", it behoves us to set our subspecific 

 lu)use in order with a view to gaining a more accurate and 

 definite appreciation of the exact rank of our subspecies, 

 and if necessary to note their quality by some definite 

 nomenclatural method. Finally, we would like to add that 

 if subspecies are sought for and recognized solely with a 

 view to the intensive study of variation, and if their recog- 

 nition tends to throw any light on the still more elusive 

 question " What is a species and how is it formed?" we are 

 all in favour of their recognition. 



P. R. Lowe. 



Natural History Museum, C. MaCKWORTH-Praed. 



12 February, 1921. 



2a2 



