Annals of the Transvaal Museum 
191 
I am of opinion, however, that one is quite as much entitled to generic rank 
as the other, and recognise some subgenera merely in order to smooth the 
way. It was my original intention to give a considerable amount of illus- 
tration to show how characters of species have changed under conditions 
of environment; but this is rather too long for the present paper and I 
have therefore given only a few, such as will be found in the Serins, Pipits, 
and a few others. It will be seen after perusing the discussion of the Pipits, 
for example, that one cannot be guided by either structural or colour 
differences as to the true relationship of the species, for we find very distinct 
groups having the same structural characters in one respect, but not in 
others, and on the other hand species which would seem to have originated 
from different stocks have come to look extraordinarily alike. And we 
find the same thing wherever we turn, the branches of the genealogical tree 
being involved in an almost inextricable tangle. We cannot in the present 
state of our progress of knowledge merely allow these deep questions to pass 
unheeded, and the first step towards answering them is to compel more 
attention to matters of detail in the specimens in the laboratory and the 
details in habits of the species. Moreover, a narrow purview will only 
hamper endeavour to find a solution to the problem of evolution, and every 
factor will have to be considered. As regards classification itself, therefore, 
some facts must be emphasised that taxonomers are apt to forget : (i) That 
the dead specimens do not always exhibit at first sight the fundamental 
difference between the species, such as voice, by which the species are able 
to recognise those of their own kind. (2) That species are guided to those 
of their kind by sight as well as voice, and that consequently colour markings 
are often more persistent than the differences in structure that come about 
by adaptations. (3) That, despite what some authors would have us believe, 
the manner of flight or ability to traverse great distances differs in the 
species from a great many causes and that the shape of the wing and tail, 
and even more so the number of feathers, are of great importance to orni- 
thological taxonomy. (4) That although the great majority of species are 
guided in procuring their food by sight, the nasal organs are frequently 
an adjunct and consequently we find this reflected in the shape of the 
external nasal characters. (5) That differences between the sexes are im- 
portant, and comparisons of species should always be made with due regard 
to the difference. (6) That age is important, albeit that the majority of 
species do not change much when once they have reached the adult state ; 
comparison of immature specimens has its utility in reference to the 
phylogeny of the species, but it is only the characters of adults that should 
be admitted for the correct diagnosing of species. (7) That in view of the 
permanence in size of the majority of species after they have become adult, 
the use of the foot-rule should be encouraged, since science is measurement 
and it would be possible by the accurate application of this measure to 
identify any species ; but naturally the drabness of investigation which the 
absolute adoption of this measure would entail is not a pleasing prospect 
and it need not therefore be reduced to refinement. Many authors seem to 
think that it is sufficient to give only the wing measurement ; but when the 
whole question is investigated it is seen that this is of only partial utility, 
and it would serve a better purpose to add the other dimensions that are 
easily taken, such as of the tail, tarsus and bill, and even the relative length 
