The most remarkable feature in their physiology is related to their 
aquatic life. One look at the skull of a crocodilian will show that the 
posterior nostrils are set so far back in the head and are so well separated 
from the cavity of the mouth by a bony palate that it is impossible for 
water to enter the breathing passages. 
A study of the circulatory system reveals the highest state of develop¬ 
ment found among reptiles. The heart is four-chambered and supplies blood 
to the head, trunk and tail through an aorta, in much the manner of higher 
vertebrates. 
The most hostile to man of the crocodilians are the crocodiles, but 
even some of these appear good-natured. A traveler in the Congo, for 
example, reported that he found two African tribes, one which ate crocodile 
meat and was eaten (whenever possible) by the crocodiles, and another 
tribe which did not use the flesh of these reptiles and was never molested 
by them. However, the authenticity of such “reciprocity pacts” is open to 
question and indicates the need for further scientific investigation. 
On occasion, when the pools and lakes which most crocodilians fre¬ 
quent in the hot months dry up, they may undertake overland migrations 
to new and wetter fields. It has been reported that in bygone days some 
towns in India were invaded by marching armies of water-seeking croco¬ 
diles. 
At mating time the sexes locate each other by bellowing and emitting 
a strong musky fluid from glands opening on the underside of the jaw 
near the throat. The females lay from twenty to ninety oval white eggs 
at a time on land where the heat of the sun or decaying vegetation hatches 
them. In some dry and sandy localities the eggs are laid in holes during 
the wet season. 
Almost all tropical countries can claim one or more species of croco¬ 
dilians. The map of crocodilian distribution shows that, although they some¬ 
times are encountered outside of the tropical zone, they are never found 
in latitudes beyond the fortieth parallel. Only the range of the alligators 
and caymans extends out of the torrid zone. 
The map is based upon researches made and published by the editor 
of this book in the Bulletin of the New York Zoological Society. 
23 
