Fast eBooks

Mr. Allen says: "The facts of the case show that a variation of from 15
to 20 per cent in general size, and an equal degree of variation in the
relative size of different parts, may be ordinarily expected among
specimens of the same species and sex, taken at the same locality, while
in some cases the variation is even greater than this." He then goes on
to show that each part varies to a considerable extent independently of
the other parts; so that when the size varies, the proportions of all
the parts vary, often to a much greater amount. The wing and tail, for
example, besides varying in length, vary in the proportionate length of
each feather, and this causes their outline to vary considerably in
shape. The bill also varies in length, width, depth, and curvature. The
tarsus varies in length, as does each toe separately and independently;
and all this not to a minute degree requiring very careful measurement
to detect it at all, but to an amount easily seen without any
measurement, as it averages one-sixth of the whole length and often
reaches one-fourth.


Pages:
91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115