106 HISTORY OF CRUSTACEA. Chap. X. 



Zoology its dogmas, whicli are as universally acknow- 

 ledged, as they are disregarded in practice. Such a 

 dogma as this is the supposition tacitly made by Agassiz. 

 Of a hundred who feel themselves compelled to give 

 their systematic confession of faith as the introduction 

 to a Manual or Monographic Memoir, ninety-nine will 

 commence by saying that a natural system cannot be 

 founded upon a single character, but that it has to take 

 into account all characters, and the general structure of 

 the animal, but that we must not simply sum up these 

 characters like equivalent magnitudes, that we must not 

 count but weigh them, and determine the importance 

 to be ascribed to each of them according to its physio- 

 logical significance. This is probably followed by a 

 little jingle of words in general terms on the com- 

 parative importance of animal and vegetative organs, 

 circulation, respiration, and the like. But when we 

 come to the work itself, to the discrimination and ar- 

 rangement of the species, genera, families, &c., in all 

 probability not one of the ninety-nine will pay the least 

 attention to these fine rules, or undertake the hopeless 

 attempt to carry them out in detail. Agassiz, for 

 example, like Cuvier, and in opposition to the majority 

 of the German and English zoologists, regards the 

 Kadiata as one of the great primary divisions of the 

 Animal Kingdom, although no one knows anything 

 about the significance of the radiate arrangement in 

 the life of these animals, and notwithstanding that the 

 radiate Echinodermata are produced from bilateral larvae. 

 The " true Fishes " are divided by him into Ctenoids 



