248 | ZOOLOGY. 
The influence of temperature upon reptiles has already been adverted 
to: we will only add that in the temperate zones many species exhibit a 
winter sleep; while this takes place in summer with inhabitants of tropical 
regions. Soft mud, with many, forms the medium in which they spend 
this period of repose. The probable effect upon the more vital functions 
consists in a sluggish and interrupted circulation, and a very slight 
respiration. Digestion must be entirely destroyed for the time. 
With regard to their geographical distribution, no reptiles whatever are 
found in the far north. They occur sparingly in the higher temperate 
regions, increasing in number to the tropics. 
The fecundity of many reptiles is very great. The frogs and toads lay 
as many as 12,000 eggs, salamanders from 10 to 40, crocodiles from 20 to © 
60, serpents 10 to 100, and turtles from 20 to 30. In some, as in many 
lizards and serpents, as well as in a few salamanders, the eggs are 
_developed before exclusion from the body. This, however, must not be 
mistaken for the viviparous placental reproduction of the mammalia. In 
most cases the eggs are laid, covered loosely with sand, mud, or leaves, and 
developed by the solar heat: in others, again, the animal itself incubates, 
as in Python tigris. Special peculiarities of reproduction will be referred 
to under the appropriate head. The external investment of the ovum may 
be simply membranous, or else calcareous: a mucous coating is found in 
the case of such species as deposit their eggs in the water. 
The number of reptiles is not fully known, new ones being described 
almost every day. Upwards of 1500 are already ascertained to exist, and 
2000 may not be beyond the maximum. The Ophidia are perhaps the 
most numerous, and next to these the Sauria; the Batrachia are more 
abundant than the Chelonia. Furthermore, while serpents preponderate in 
torrid regions, the batrachians are more properly inhabitants of the tem- 
perate zone. Thus, in North America alone there are upwards of 80 
species, 50 of them belonging to the wrodelian, or tailed forms. 
Reptiles Jive partly on land alone, partly in water alone; others, again, 
occupy either indifferently, or at different times of the year. For this 
reason, the latter have received the name of Amphibia from some zoolo- 
gists. | 
The flesh of reptiles is not used as food to any great extent, although 
there is no doubt of its extreme excellence in many cases. In various 
parts of the world, however, serpents, large saurians as the iguana and 
alligator, turtles, frogs, &c., are favorite articles of food. The eggs of 
turtles, and of the iguana, are highly prized. They are extracted, by some 
South American tribes, from the oviduct of the living iguana, without any 
serious injury to the animal. The shell of the Chelonia imbricata, or 
hawks-bill turtle, furnishes the tortoise-shell of commerce. The teeth of 
the alligator furnish ivory of an excellent quality. Beyond these instances 
but little economical value attaches to reptiles. 
45% 
