234 SCIENTIFIC THOUGHT. 



organs in living beings, and their functions. In plants, 

 these organs and functions seemed to be much simpler 

 and more easily observed than in animals, and Linnaeus 

 had selected the sexual organs, since they were the most 

 easily distinguishable, as a primary character for his 

 classification of the vegetable kingdom. Somewhat 

 later l he classifies the animal kingdom according to the 

 internal structure, and characterises animals for the 

 purpose of division according to the heart and the blood. 

 The celebrated dictum, that " minerals grow, plants grow 

 and live, animals grow, live, and feel," which appeared in 

 the last edition of the ' Systema Naturae,' places a physio- 

 logical distinction at the base of the classification. This 

 conception, which has been somewhat modified since 

 Linnseus's time to meet our altered views, is an obvious 

 first step towards a description of natural objects. Yet 

 this no more than the second step, which fastens upon 

 the organs of reproduction in plants, on the heart and 

 blood in animals, gives any clue to the comprehension 

 of the great variety and apparent fixity of forms which 

 the living world presents to our observation. In fact, 

 purely morphological considerations were subordinated to 

 physiological ones, and were brought in only to assist 

 in the further subdivision of the two great kingdoms. 

 Linnaeus felt the artificiality of his classification the 

 arbitrariness of the characters he selected for the pur- 

 pose of division. But a more natural system could only 

 be arrived at by an intimate knowledge of and intercourse 

 with living nature, as well as by a careful comparison of 

 its hidden forms and organisation i.e., by a more de- 



1 See Carus, ' Geschichte der Zoologie,' p. 503, Ac. 



