wonderful modification of structure the female exhibits only a
rudiment. Again, in Chamaeleo Owenii (Fig. 36), from the West Coast of
Africa, the male bears on his snout and forehead three curious horns,
of which the female has not a trace. These horns consist of an
excrescence of bone covered with a smooth sheath, forming part of the
general integuments of the body, so that they are identical in
structure with those of a bull, goat, or other sheath-horned ruminant.
Although the three horns differ so much in appearance from the two
great prolongations of the skull in C. bifurcus, we can hardly doubt
that they serve the same general purpose in the economy of these two
animals. The first conjecture, which will occur to every one, is that
they are used by the males for fighting together; and as these animals
are very quarrelsome (69. Dr. Buchholz, Monatsbericht K. Preuss.
Akad. Jan. 1874, p. 78.), this is probably a correct view. Mr. T.W.
Wood also informs me that he once watched two individuals of C. pumilus
fighting violently on the branch of a tree; they flung their heads
about and tried to bite each other; they then rested for a time and
afterwards continued their battle.
With many lizards the sexes differ slightly in colour, the tints and
stripes of the males being brighter and more distinctly defined than in
the females. This, for instance, is the case with the above Cophotis
and with the Acanthodactylus capensis of S. Africa. In a Cordylus of
the latter country, the male is either much redder or greener than the
female. In the Indian Calotes nigrilabris there is a still greater
difference; the lips also of the male are black, whilst those of the
female are green. In our common little viviparous lizard (Zootoca
vivipara) the under side of the body and base of the tail in the male
are bright orange, spotted with black; in the female these parts are
pale-greyish-green without spots. (70. Bell, History of British
Reptiles, 2nd ed., 1849, p. 40.) We have seen that the males alone of
Sitana possess a throat-pouch; and this is splendidly tinted with blue,
black, and red. In the Proctotretus tenuis of Chile the male alone is
marked with spots of blue, green, and coppery-red. (71. For
Proctotretus, see Zoology of the Voyage of the Beagle ; Reptiles, by
Mr. Bell, p. 8. For the Lizards of S. Africa, see Zoology of S.
Africa: Reptiles, by Sir Andrew Smith, pl. 25 and 39. For the Indian
Calotes, see Reptiles of British India, by Dr. Gunther, p. 143.) In
many cases the males retain the same colours throughout the year, but
in others they become much brighter during the breeding-season; I may
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