280 THE HARMONIES OF NATURE. 



Its business is to restrain the undue increase of the smaller birds 

 by devouring their eggs. Now, if the teeth had existed of the 

 ordinary form and proportion in the jaws and palate, the egg 

 would have been broken as soon as it was seized, and much of 

 its nutritious contents would have escaped from the lipless 

 mouth of the snake in the act of deglutition ; but owing to the 

 almost edentulous state of the jaws, the egg glides along the 

 expanded opening unbroken ; and it is not until it has reached 

 the gullet, and the closed mouth prevents any escape of the 

 nutritious matter, that the shell is exposed to instruments 

 adapted for its perforation. These instruments consist of pro- 

 cesses growing out of the last cervical vertebrae, the extremities 

 of which are capped by a layer of hard cement, and penetrate 

 into the interior of the oesophagus. The shell being sawed open 

 longitudinally by these vertebral teeth, the egg is crushed by the 

 contractions of the gullet and is carried to the stomach, where 

 the shell is no doubt soon dissolved by the acid gastric juice. 



The intellectual powers of the reptiles are confined to very 

 narrow limits, yet these lowminded animals possess many of the 

 passions and instincts which we have had occasion to observe 

 among the fishes. The same imperative impulse which forces 

 the salmon to quit the salt -waters of the ocean and ascend the 

 rivers, compels also the turtles at the beginning of the dry season 

 to seek the sandy shores of desert islands or solitary bays, or 

 directs the marsh and river-tortoises to the warm flat islands 

 which dot the surface or crowd about the estuaries of the colossal 

 tropical streams. There they select a place in which their eggs 

 can be hatched by the heat of the sun, and dig holes before 

 depositing them for their protection. As soon as they burst 

 their shell, the young immediately crawl towards the water, 

 in obedience to the instinct which tells them that this is their 

 proper element, and that the dry sands, after having once done 

 their office in bringing them to life, can afford them neither 

 security nor food. 



The lacertine and ophidian tribes also select proper places for 

 their eggs, either in the warm sand or in heaps of fermenting 

 substances. Thus several of the American alligators, after having 

 scraped together a little mound on the banks of rivers, hollow it 

 out in the middle and fill up the rest with vegetable matter, as 

 if a professor of chemistry had taught them that the process of 



