62 THE VIVARIUM. 
they may happen to find within the Reptiles. Frequently a 
Crocodile or an Alligator haunts a particular portion of a river, 
and seems to look upon all the neighbourhood within certain 
limits as belonging to himself, nor will he brook any intrusion 
upon the part of his fellow Crocodiles or Alligators. Should he 
die, however, another is sure to take his place. 
When one of these Reptiles is floating quietly in the water, 
with only his eyes and nostrils just above its surface, he is very 
likely to escape the observation of the unwary ; hence it is that so 
many people fall victims to these hungry beasts. 
Kvery member of the Crocodilia possesses three eyelids to each 
eye. The nictitating eyelid is closed when the animal goes under 
water, and prevents that element from entering the eye; but, 
being transparent, allows the Reptile to see. I have noticed that 
this membrane is also frequently drawn over the eyes as the 
creature basks in the sun. While under water, besides closing 
the nictitating eyelids, it covers its nostrils by means of valves 
provided for that purpose, and folds a flap or lid of skin over the 
entrance to each ear. In addition, when this creature has seized 
a victim with its long, sharp, and conical teeth, and dragged it 
under water to drown it, it is able, by using certain membranes, 
to prevent the water from running down its own throat. 
The Crocodilia, because of the narrowness of their throat, are 
obliged to tear their prey to pieces before swallowing it; hence 
they frequently break or wear away their teeth. However, they 
do not suffer from the loss owing to an interesting provision of 
nature. Hach tooth is hollowed at its base and so is able to 
receive the germ of a new tooth. And between the germ and the 
tooth in use, there is a third, which is sheathed in the latter, 
covers the former, and is ready for work as soon as required. 
According to the country, some Crocodiles and Alligators 
hibernate in the winter, and others estivate, in mud, during the 
drought of summer. 
_ All the Crocodilia are oviparous, and the hard calcareous eggs 
which they lay are very small (not larger than those of the 
turkey) in comparison with the ultimate size of the animals which 
are to come from them. For instance, Dr. Giinther, in ‘‘ The 
Reptiles of British India” says that ‘‘ Jerdon has reported a case 
