266 ZOOLOGICAL PHILOSOPHY 



animals, at which some organ began to exist, in order to save ourselves 

 from seeking that organ in much earher points of the order. Other- 

 wise science would be retarded by our hypothetically referring to parts 

 with which we are little acquainted, faculties which they could not 

 have. 



Thus several botanists have made useless attempts to find sexual 

 reproduction in agamous plants (the cryptogams of Linneeus), and 

 others have thought that they had found, in what are called the tracheae 

 of plants, a special organ for respiration. In the same way several 

 zoologists have wanted to prove the existence of lungs in certain 

 molluscs, a skeleton in star-fishes, gills in jelly-fishes : lastly, a learned 

 society has this year set, as a prize subject, the question whether there 

 exists a circulation in radiarians. 



Such attempts prove indeed how httle we are yet impressed by the 

 natural order of animals, by the progress in the complexity of their 

 organisation, and by the general principles which result from the 

 knowledge of that order. In a matter of organisation, moreover, 

 when the objects dealt with are very small and unknown, people 

 think they actually see what they want to see, and they thus find 

 whatever they want : as, for instance, already happens in the arbitrary 

 reference of faculties to parts of whose nature and function we are 

 ignorant. 



Let us now enquire what are the chief faculties peculiar to certain 

 living bodies and let us see at what point in the natural order of animals 

 and plants each of these faculties, with its attached organ, began to 

 exist. 



The chief of the faculties peculiar to certain living bodies, and con- 

 sequently not shared by the rest, are as follows : 



(1) The digestion of food ; 



(2) Respiration by a special organ ; 



(3) The performance of acts and movements by muscular organs ; 



(4) Feeling, or the capacity for experiencing sensations ; 



(5) Multiplication by sexual reproduction ; 



(6) A circulation of their essential fluids ; 



(7) The possession of a certain degree of intelUgence. 



There are many other special faculties, of which examples are found 

 among living bodies and especially among animals ; but I shall con- 

 fine myself to the consideration of these few, because they are the most 

 important, and because what I have to say about them is sufficient 

 for my purpose. 



The faculties which are not common to all living bodies are based 

 in every case without exception on special organs which cause them, 

 and hence on organs that are not possessed by all living bodies ; and 



