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(whether temporary or permanent) of these and other lizards to 
the sole influence of light, acting directly on the deeper cells of 
the skin and causing them to assume a more superficial position. 
Leydig has sufficiently disposed of this explanation. Our space 
does not allow us to cite the details of his very interesting and 
convincing observations. 
All the actions of the Chamaeleon, except during the breeding 
season, tend to the procuring of food. The tongue is the pre- 
hensile organ used for this purpose. A Chamaeleon projecting 
its tongue may truly be designated the entelechy, or perfection, 
of the living animal. 
When not thus employed, the tongue lies concealed in a 
special depression of the floor of the mouth. We must there- 
fore distinguish its retracted from its extended condition. 
Brehm rightly indicates a third, or intermediate, phase, in 
which the tongue, previous to being ejaculated, is loosened 
and pointed towards its prey. 
The tongue consists of two principal regions, a proximal and 
a distal. The former, or so-called ‘ worm/ is exceedingly ex- 
tensile, but is much shortened in the retracted condition. The 
latter is terminal and club-shaped, preserving in its alternate 
states nearly the same dimensions. Milne-Edwards distinguishes 
a basal division, behind the worm, which may rather be said to 
consist of the hyoid muscles. These are very complicated. A 
full technical description of them would be out of place in the 
present paper. 
The worm is not inaptly so termed, whether we view it in 
its retracted or extended state. In the former, it is much cor- 
rugated transversely, and is about as long as the ‘club / the 
whole tongue having an average length of an inch and a half. 
When fully stretched out, to an extent of some five inches, the 
worm is nearly smooth. A trifling fold still distinguishes it 
from the club, into which it passes by a gradual enlargement. 
The club is bilobed, with an upper and a lower ‘ lip/ The 
extremity of the latter projects in front of the tongue, and its 
ventral aspect is plainly more elevated than that of the club 
lying behind it, from which it is marked off by an indentation. 
The upper lip, or ‘ dome ’ of Mr. Salter, is itself shaped like a 
tongue in miniature, having a raised dorsal surface, the gently 
narrowed hinder portion of which descends rather abruptly to 
join the club proper. From this part to its anterior end the 
dome is more than half as long as the club. The shallow fissure 
between the two lips is dilated into a funnel-shaped cleft by 
their separation when the tongue is thrown forwards. 
A glutinous secretion lubricates the club, which has minute 
