CLASSIFICATION IN THE ANIMAL KINGDOM. 



27 



Amphibia, whilst possessing striking peculiarities of their own, both 

 external and internal, and in general appearance more resembling 

 Reptiles, yet in their early embryonic development agree with Fishes 

 in opposition to all the higher classes, seems to me decisive as to their 

 distinct position. 



On the second sub-kingdom, Articulata, I need make but few re- 

 marks. I agree entirely with Dr. Dawson in placing Arachnida as the 

 first, or what he calls the nervous class, which manifests the highest 

 development of which the type is capable, and I am pleased to have 

 his support in this view in opposition to the misleading influence of a 

 false analogy. 



I differ from Dr. Dawson in believing that the predominance of the 

 Nutritive system, is expressed by two different plans of development, 

 thus introducing a fifth type of structure. The one tending to fulness 

 of figure and the use of the ordinary modes of appropriating food, but 

 without violence being required for the purpose, and accompanying 

 terrestrial habits of life when at all suited to the prevailing structure ; 

 the other tending to an elongated figure, to a suctorial or anomalous 

 mode of appropriating food, and, usually, to semiaquatic habits of 

 life. Of course I regard Worms (Annulata) as the second nutritive 

 type, and the question with me is, whether a fifth great group can be 

 found in the sub-kingdom, suitably representing Dr. Dawson's embry- 

 onic or reproductive class. Now those who have read a few of the 

 popular works on Zoology will have been asking themselves how it is 

 that Dr. Dawson's arrangement overlooks the Rotatoria or Rotifera — 

 the wheel animalcules to which their attention has been directed in 

 those works. We must presume that he has thought that they 

 might be treated as low forms of Annulata or Crustacea, and having 

 thus disposed of them to his satisfaction has not felt obliged to speak 

 of them in so general a view of the subject as his paper offers. 

 Nevertheless, the characters of the class are very clear and definite ; 

 the discussion which has been carried on by eminent zoologists as to 

 its nearer relationship to Crustacea or Annulata have served to estab- 

 lish its distinctness from both, whilst proving its direct affinity espe- 

 cially with the latter ; and whatever may seem rudimentary in its 

 structure especially suits its position as the embryonic class in its 

 sub-kingdom. There are so many high authorities for its being 

 considered as a class, that at present I need do no more than point 



