192 
ZOOLOGY. 
The poisonous snakes stand lowest in tlie series; tliey arc 
succeeded by tlie striped snake, milk adder, and by the 
boas, which attain a length of five metres; while the ana- 
conda grows eight metres long. 
Order 2. Lacertilia, — Most lizards have cylindrical bodies, 
usually covered with small overlapping scales, with a long, 
slender tail, and generally two pairs of feet, the toes long 
and slender, and ending in claws. They run with great 
rapidity, and are active, agile creatures, adorned with bright 
metallic colors, in some cases green or brown, simulating 
the tints of the vegetation or soil on which they live; some 
are capable of changing their color at will, as in the chame- 
leon and Anolis; this is due to the fact that the pigment 
cells (chromatophores) are under the influence of the vol- 
untary nerves. 
In many lizards {Lacerta, Iguana, and the Geckos), the 
middle of each caudal vertebra has a thin cartilaginous par- 
tition, and it is at this point that the tails of these lizards 
break off so easily when seized. In such cases the tail is 
renewed, but is more stumpy. 
Both jaws are provided with teeth, while some have them 
developed on the bones of the mouth. The teeth are usu- 
ally simple, sharp, conical, as in most lizards, including the 
Monitor, or they are flattened, blade-like, with serrated 
edges, as in the Iguana, or as in Cyclodus they are broad, 
adapted for crushing the food. Most lizards prey on in- 
sects; some live on plants. The eyelids are well-developed 
except in the Geckos, in which the lids are modified some- 
what, as in the snakes, to form a transparent skin over the 
cornea of the eyes. The tongue is free and long, some- 
times forked; in the iguana it ends in a horny point. 
While the limbs are usually present, one or the other 
pair may in rare cases (in Pseiidopus the fore feet are 
wanting; in Chirotes the hind feet are absent) be absent, 
or as in Ampliisicena and its allies the feet are entirely 
wanting. 
Lizards lay their eggs in the sand or soil. The iguana 
