THE AUSTRALIAN NATURALIST. 139 
possible, to questions of a general nature, likely to be of interest 
to members of the ‘Club; anda number of lantern views will 
show peculiar variations in form, structures adapted to environ- 
ment, interesting points in distribution, interesting habits, etc. 
In giving a short account of some of the more important or 
interesting families of lizards, the peculiar variations in form 
exhibited by the various members of the group will be touched 
upon, but in ‘the meantime, a few general remarks may be 
made in'regai'd to the striking adaptation to surroundings that 
many of these variations show. 
According to the diet, we find the teeth and the alimentary 
tract variously modified, e.g., in carnivorous forms the intestine 
is relatively short, while it is long in the vegetable feeders. 
This correlation is found not only in lizards, but in most 
vertebrates, The tongue, which is often used for picking up the 
food, 1s variously modified, and often takes the form of an 
effective shooting organ, capable of being shot ont several 
inches, dabbing insects and the like with great precision. It 
is interesting to note that in one genus of lizards, Helcderma, 
the salivary glands are modified into poison glands, and the 
teeth grooved. . 
But most of the adaptive modifications are restricted to the 
external organs such as the skin, limbs, tail, eyes. Most 
lizards are capable of changing the colour of their skin to a 
certain extent, the stimulus being through the emotions. In 
regard to the limbs. and the shape of the body, we find forms 
specially adapted for climbing or running swiftly, or burrowing 
in the ground, or'even flying. The flight, however, is not of an 
active nature; ‘the wing-like structures are used as a parachute, 
enabling the owner to sail downwards and outwards a consider- 
able distance. 
In the Zoologische Garten, 1889, Boettger Has published some 
very interesting ‘work on the influence of climate and the 
nature of the country on the animals inhabiting it, with special 
reference to a particular region—the Transcaspian desert region. 
Dr. Gadow gives an ‘excellent synopsis of this work in the 
Cambridge Natural ‘History, in his volume on Amphibia and 
Reptiles; and I wish here to express my special indebtedness 
to Dr. Gadow’s work in'the preparation of this address. 
In the 'ranscaspian desert the winter is short but very 
severe, while ‘the summer is ‘prolonged and extremely hot. 
There‘are no'trees and hardly any shrubs, and most of those 
‘that, do oceur haye'narrow, grass-like blades for leaves. Little 
mounds of earth and sand surround the shrubs, and these little 
shelters form.a'retreat for lizards, snakes and rodents. 
Adaptations to this peculiarly inhospitable environment are 
‘strikingly shown in some of the lizards. 
~The Geckos-are-a family of lizards occurring all over the 
world, and they are generally found climbing about rocks or 
