28 



THE YOUNG NATURALIST. 



each case the organ is perfect in its utility, and is but a modification of the 

 same structure. Analogous cases occur amongst reptiles, as in the tongue of 

 the chameeleon, which can be protruded to a distance equal to the length of 

 the animal's body, and has at its free extremity, a clubbed and sticky pro- 

 tuberance, with which it secures its insect prey. Again, in geckos the feet 

 have developed suckers, which enable them to walk upside down on over- 

 hanging rocks, and on the roofs of caverns or on ceilings in chase of insects. 



The more highly organised the adult, the more helpless the young. This 

 seems the universal law of nature. It is familiar to us in the mammals, so 

 familiar as to be sometimes lost sight of : but it is startling to find the same 

 law ruling amongst the Sauropsidans. Many of the birds whose powers of 

 flight have been almost, if not quite lost, lay their eggs and leave them to be 

 hatched by the heat of the sun, just as the reptiles do ; and also as in the 

 reptiles, the young when hatched out are' able to fend for themselves. In the 

 highest developed birds, the young, when hatched are almost helpless, and 

 depend for existence on their parents' care, which also provides for them, in 

 most cases, a comfortable nest. As we have shewn that in the great rep- 

 tilian epoch, none but flying birds could maintain the struggle for existence ; 

 we must also assume, that owing to similar causes, they were compelled 

 to be nest-builders, and to develope the hind toe for grasping, as in the 

 passerine birds ; and we must therefore take it, that, as the existing non- 

 flying birds present reptilian characteristics in the more perfect development 

 of their young, when newly hatched, so their ceasing to build nests (which at 

 an earlier geological period were necessary for the preservation of the species), 

 is but another proof, were that needed, that they are a reversion, in reptilian 

 direction, from their flying ancestors. 



Before concluding, we may briefly recapitulate the main points in this 

 argument viz : — 



Connecting link between batrachians and reptiles. Some Chelonians 

 having internal gills, and the Alpine black salamander becoming viviparous. 



Snakes undoubtedly are lizards which have lost their limbs through disuse. 



Early in the Secondary period development amongst reptiles in the direc- 

 tion of flight seems to have been going on, on several divergent lines. This 

 is evident from the fact, that Plerosauria are contemporary with earliest birds. 



It is sometimes assumed that running birds are the ancestors of flying 

 birds. This is certainly erroneous. No running birds which were not at the 

 same time good flyers, could have maintained the struggle for existence 

 against such foes as the Pterosauria. 



The young of all reptiles are able to provide for themselves immediately at 

 birth, so are also the young of our running birds — clearly pointing to the 



