§ 22. ORGANIZATION OF REPTILES. 569 



blood, they dive with facility, and remain under water for a 

 long period without inconvenience. Some are viviparous, 

 others are oviparous, laying their eggs, which they never 

 hatch, on the sands or banks. They present great diversity 

 of form ; some are extremely elegant, others grotesque and 

 hideous, and many have dermal processes of the most 

 fantastic shapes. Their habits are exceedingly variable ; 

 some are agile, others torpid ; all hibernate, or rather 

 relapse periodically into a state of dormancy, whether pro- 

 duced by cold, drought, or excessive moisture. Their 

 peculiar structure enables them to endure long abstinence, 

 to an extent impossible to other races of animals. Their 

 seasonal habits, or, in other words, alternate periods of 

 activity and repose, are in accordance with the sudden 

 evolutions of the seasons ; they are dormant when nature 

 does not need their agency, and rouse into activity when 

 required to repress the redundancy of those vegetables or 

 animals which constitute their food ; a property strikingly 

 manifest in the species of hot climates ; thus exhibiting an 

 admirable adaptation to the peculiar conditions of existence 

 which they are destined to fulfil. Some are herbivorous, 

 others carnivorous, and many prey on insects ; their powers 

 of progression are as various ; some orders, though destitute 

 of fins, wings, or feet, bound along the ground with great 

 agility ;* others walk or swim ; while a few are capable of 

 flight.f 



24. Turtles, or Chelonian Reptiles. — In Turtles the 

 want of active faculties is compensated by their passive 

 means of resistance. They have no weapons of offence, but 

 are enclosed in a panoply of armour formed by the expan- 

 sion of the ribs above, and by the bones of the chest beneath. 

 The carapace, or buckler, constituting the shell that spreads 

 over the back of the turtle, is composed of the ribs, which, 

 instead of being separated by intervals, as in other animals, 



* The Serpents. f The Draco volans, or Flying Dragon. 



