THE LIVING WORLD. 
J 59 
that its power to bite is very great, though indisposed to exercise this pro¬ 
tective provision. The only excitement the animals exhibited under the provo¬ 
cation which I gave them, was by emitting a slight hissing noise, but though 
I examined carefully, no appearance of any liquid on the sticks thrust into their 
mouths was visible. My conclusions, founded upon my experience and such 
•experiments as Dr. Shufeldt Reports, therefore are, that the animal may secrete 
a poisonous fluid from its maxillary glands, such secretion being very like that 
secreted by other batrachians, but that the power to use this venom is so seldom 
■exercised that the animal is hardly deserving of the reputation given to it by 
Dr. Shufeldt and Prof. Kingsley. 
The heloderma is of a dirty brown color, thickly covered with small yel¬ 
lowish spots. The skin is rough and hard, coated with horny tubercles. Its 
head resembles that of the toad except the crown covered with prominent tubercles, 
which add much to its repulsiveness. The legs are strong and body and tail 
thick, around the latter being indistinct rings of pale yellow. It lives off insects, 
and burrows in the sand during the rainy season. I have never seen a specimen 
that exceeded fifteen inches in length, and am doubtful of the claim that they 
occasionally grow to be much larger. 
THE CROCODILE, OR TORTOISE LIZARD. 
SAURIANS OF THE ANCIENT WORLD. 
From a consideration of the batrachian , the frog, and the lacertilian , or lizard, 
species, we come next and most naturally to the crocodilia , or crocodile species 
of reptiles, which is the next step in the progressive order of creation. As 
already stated, in the preliminary remarks introducing the division of reptiles, 
•development in nature has been rather towards diminution in size in nearly all 
species to accommodate them to the changes which a gradual cooling of the 
earth produced. We find nature most prodigal in tropical regions, where vege¬ 
tation is not only rankest but where animal forms of life are largest and most 
numerous. Should the temperature of the ea^th grow one degree cooler each 
year at the tropics we would perceive a gradual change taking place in the size 
and forms of life there, both vegetable and animal; for, as vegetation became 
less rank food would become less plentiful, when, in the reciprocal relations 
invariable in nature, to compensate by adaptation, animals would as gradually 
diminish in size, the larger becoming extinct first or dwarfing in proportion and 
appetite, so that their demands might not be greater than nature could supply. 
At a period when the earth was nearly covered with warm waters the condi¬ 
tions were favorable to creatures of most extraordinary proportions, as compared 
with animals of to-day, and to this enormity of size was added the most terrible 
and ferocious aspects. Herein we perceive another rule of nature, established in the 
beginning and prominent still even to the most casual observer, viz., that fero¬ 
city in animal kind is usually proportionate to the size of the creature. That 
there are exceptions to this rule we must freely admit, yet generally it is as 
invariable as rules most commonly are, so true, indeed, that the exceptions serve 
to emphasize its verity. 
The age of fishes being followed by that of reptiles, we find the creatures 
thus adapted to life either in or out of the waters, of gigantic proportions, and 
being diverse as well as immense, their armaments were commensurate with their 
