CLASSIFICATION IN THF ANIMAL KINGDOM. 29 



I have named the three classes into which they may be divided. I 

 have also given a reason why it seems to me reasonable to expect only- 

 three instead of five classes in the two lower sub-kingdoms in which 

 there can hardly be said to be any special development of the powers 

 of sense and motion, the nutritive and reproductive systems com- 

 pletely predominating. If it were allowable on this occasion to enter 

 on details respecting the sub-divisions of the classes, I could easily 

 show, as I have on other occasions endeavoured to prove in this place 

 in respect to the more important classes of Vertebrates, that the 

 number five, not three, four, seven, or any other that has been pro- 

 posed, is the number of natural tendencies appearing, and continually 

 repeating themselves in the divisions of the animal kingdom, and thus 

 producing the order which prevails throughout nature. Our author's 

 seventh and last section relates to the division of classes into orders 

 and families. I have already referred to the higher of these divisions, 

 objecting to the opinion that grade or rank has any special appropri- 

 ation as a character to orders, and I may add that I assign more 

 importance to families, and regard them as more definite groups, than 

 Dr. Dawson appears to do. It is an ingenious idea that the distinctive 

 characters of orders in each class are mainly derived from the function 

 which the class represents, " for example, the orders of Birds, Insects, 

 Gasteropods, and Acalephse should be ascertained chiefly by reference 

 to the locomotive organs as being the system of organs most eminently 

 represented in the class," but I question its being in strict conformity 

 with facts, since on the one hand the organs of motion have been 

 much employed as class characters in the sub-kingdom Mollusca, 

 which is the reverse of being specially concerned with motion, and on 

 the other, I must hold it to be reasonably denied that either Gas- 

 teropods or Acalephse at all represent the motive tendency, and granting 

 that they did so, and omitting to insist now on the Pteropods being 

 a genuine class, what can be said of a sub division of Gasteropoda 

 which does not recognise as orders Pulmonata, Siphonophora, and 

 Holostomata. The orders of Insecta generally received ars exceed- 

 ingly unsatisfactory, and demand revision, and those of birds depend 

 more on the kind of food and mode of securing it as indicated by the 

 structure of the beak and feet than on the proper motory organs. 

 In most cases, it appears to me, where grade or rank is a special 

 ground of distinction it leads us to sub-classes, represented by con- 

 centric circles, in each of which we find corresponding sets oi Jive 

 orders, representing in their degree the five tendencies. 



