Letters , Extracts , and Notes. 
34 7 
1921.] 
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—given favourable conditions. Mutational variations 
in 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 propounded by Mr. Loomis “ Of what scientific 
value is a subspecies?”, it behoves us to set our subspecific 
house 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, G. Mackworth-Praet>. 
12 February, 1921. 
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