24 Darwin, and after Darwin. 



order to classify them scientifically ; and, also, that 

 for this purpose the internal parts were of quite as 

 much importance as the external. Indeed, he per- 

 ceived that they were of greatly more importance in 

 this respect, inasmuch as they presented so many 

 more points for comparison ; and, in the result, he 

 furnished an astonishingly comprehensive, as well as 

 an astonishingly accurate classification of the larger 

 groups of the animal kingdom. On the other hand, 

 classification of the vegetable kingdom continued 

 pretty much as it had been left by the book of Genesis 

 all plants being divided into three groups, Herbs. 

 Shrubs, and Trees. Nor was this primitive state of 

 matters improved upon till the sixteenth century, when 

 Gesner (1516-1565), and still more Caesalpino (1519- 

 1603), laid the foundations of systematic botany. 



But the more that naturalists prosecuted their 

 studies on the anatomy of plants and animals, the 

 more enormously complex did they find the problem 

 of classification become. Therefore they began by 

 forming what are called artificial systems, in contra- 

 distinction to natural systems. An artificial system 

 of classification is a system based on the more or less 

 arbitrary selection of some one part, or set of parts ; 

 while a natural classification is one that is based upon 

 a complete knowledge of all the structures of all the 

 organisms which are classified. 



Thus, the object of classification has been that of 

 arranging organisms in accordance with their natural 

 affinities, by comparing organism with organism, for 

 the purpose of ascertaining which of the constituent 

 organs are of the most invariable occurrence, and 

 therefore of the most typical signification. A porpoise, 



