CHAMELEONS. 
109 
following points of difference between the percipient layer of 
the Chamaeleon and that of man. 
1. The Chamaeleon has no rods, but cones only. 
2. The foveal cones in the Chamaeleon are remarkably 
thinner than in man. 
3. The (absolute) length of the foveal cones in the Cha- 
maeleon, notwithstanding its smaller eyes, is more 
conspicuous than in man. 
4. The difference in the diameter of the cones, both in the 
peripheral and central regions of the retina, is greater 
in the Chamaeleon. 
5 The region corresponding to the human yellow spot is 
more extensive in the Chamaeleon. 
On the whole, sums up H. Muller, if we compare the human 
eye with that of the Chamaeleon, the reptile has altogether the 
advantage. 
Outside the bulb of the eye, but within the large though 
shallow orbit, the optic nerve, which is here remarkably long, 
makes a complex loop. It bends downwards, outwards, and 
again upwards (or even inwards, in certain positions of the eye), 
previous to its insertion. 
Retractor muscles of the eye appear to be absent. 
There is a large Harderian gland at the anterior angle of 
the eye, although the nictitating membrane is rudimentary. 
The lachrymal gland is small. 
The two eyelids of man are represented by one great circular 
curtain, drawn over nearly the whole periphery of the protruding 
bulbus and circumscribing a small central orifice. A bony 
plate lies in the lower moiety of this lid. Beneath the skin of 
the lid, which resembles that of the general surface, is spread 
an extensive orbicularis muscle. 
The free surface of the conjunctiva, very distinct from the 
adjoining lid, is also of unusual extent, reaching as far back as 
the equator of the bulb. The extraordinary mobility of the 
Chamaeleon’ s eyes, in which it far surpasses all other vertebrates, 
is much aided by this arrangement, to which the curious cur- 
vature of the long optic nerve also contributes. 
Thus, whether we consider the eye itself or its appendages, 
we have to do with an apparatus which is without parallel in 
the animal kingdom. 
The male of the common Chamaeleon differs but slightly 
from the female. He is known by his occipital crest, which is 
longer and higher, and by the shorter fold occupying the region 
of the neck. 
The female lays a heap of sphacroidal eggs, grayish- white in 
tint, with calcareous, very porous shells. Oviposition has been 
