CROCODILL.S AND SNAKES 



267 



which shall apply to all alike. \\'c have already seen what a wonder- 

 ful dilTercnce there is hetween such nianmials as the hat and the lion, 

 the monkey and the whale, or the elephant and the mouse; but even 

 between creatures so very unlike one another as these, there is still a 

 great resemblance in many important ways. They all, for instance, 



\ A 



BLACK- CROCODILE 



possess four limbs, and I heir young, with one single exception, are all 

 born alive, while ihcy always breathe air itself, and never respire 

 water by means of gills. 



But in the case of the Reptiles we find no such rules as these. 

 Some have four legs, and others none. Some lay eggs, and some pro- 

 duce li\'ing young. Some 1)reathe air, and some breathe water, so that 

 it is really almost impossible to draw up a description which shall be 



