56 THE PRESENT. 



ranked so high as the mammal that brings forth its young 

 alive, and even then, by a special organisation, suckles 

 them during months with assiduous care. But on such 

 distinctions we need not dwell. They were made long be- 

 fore observation had shaped itself into systems of science, 

 and are patent alike to the learned and the unlearned. 

 This dictum, therefore, the zoologist lays down, that the 

 loiver a creature is in the scale of being, the more its indi- 

 vidual parts resemble each other (vegetative repetition) ; and 

 the higher it is, when, instead of several functions being per- 

 formed by the same organ, each function, be it of nutrition, 

 reproduction, or sensation, is performed by an organ speci- 

 ally devoted to it. 



This brings us to the classification of the zoologist ; and 

 in comparing the Past with the Present Life of the Globe, 

 the paleontologist requires to invent no new system or 

 scheme of arrangement. One plan and design runs through 

 the whole of animated nature ; and though species and 

 genera, and even whole families, have died out, and others 

 have taken their places and this has been repeated again 

 and again still have all the successive incomers been con- 

 structed upon the same plan, and designed to perform ana- 

 logous functions. The classification of the palaeontologist 

 is therefore the same as that of the zoologist, with the 

 exception of such extinctions as fill up the gaps that exist 

 between conterminous genera, and render more compact 

 and harmonious, if we may so speak, the grand scheme of 

 terrestrial vitality. The following outline of the animal 

 kingdom will render more intelligible the comparisons we 

 have to institute betAveen the past and the present be- 

 tween the forms that now live and act, and those that 

 have become extinct and been converted into stone thou- 

 sands of ages ago : 



