214 THE RELATIVE RANK OF 



CHAPTER XII. 



ARTICULATA. 



THERE is one feature in the organization of Articulata, and 

 indeed the most prominent one, which would appear to be 

 strongly demonstrative that this grand division ought to be 

 classed in a lower rank than that of Mollusca. I refer to the 

 repetition of similar parts in Articulata, as contrasted with the 

 total absence of this character in Mollusca. Were it confined 

 to the exterior, we might ascribe to it a merely functional char- 

 acter, a jointing of the shelly or parchmenty covering in order to 

 produce a complete flexibility of the body ; but, as we find it 

 equally conspicuous among the internal organs, the intestines, 

 heart, lungs or gills, nervous system, and the reproductive sys- 

 tem, one cannot avoid the conclusion that it is typical of the 

 whole organization. 



As it has already been shown (pp. 82, 84) that in many cases 

 this repetition of parts is merely the multiplication of a kind of 

 obscure individuality, it may be said, in a not very far-fetched 

 sense, that the group of Articulata is composed of compound 

 individuals, whereas the group of Mollusca, hardly excepting 

 the Bryozoa, Tunicata, and Salpas, consists of single individuals, 

 which possess the utmost uniformity of organization. It is true 

 that the Articulata progress far in that direction ; but yet the 

 highest of them, the Insects, do not attain to that singleness of 

 character which exists even in the lower middle ranks of Mol- 

 lusca. But as this is not the only available character by which 

 we may judge of the point in question, and as there is a more 

 universal and elevated quality, which, under the form of instinct, 

 is so much more highly developed among the immense numbers 

 of the superior ranks, the Insects and Spiders, we can hardly 

 refrain, from a psychical point of view, from classing the Ar- 



