242 Agassi^ Contributions to the 



The very attempt thus to attach a scientific value' to these divi- 

 sions is a great step in advance; for, though such distinctions 

 have almost instinctively fixed themselves more or less strongly 

 on the minds of naturalists, no one has- given them full and formal 

 expression as Agassiz now does. The attempt, however, is full of 

 difficulty ; and, as might have been anticipated, — and as the au- 

 thor himself fully and modestly admits, — must be regarded as very 

 imperfectly successful; though the whole doctrine of type and 

 homology in nature implies that there must be a definite grada- 

 tion of groups. Let us examine it in detail ; and, in doing so, 

 we would wish to direct the attention of students in natural his- 

 tory to a careful consideration of the subject as set forth in the 

 work itself. 



1. Following Cuvier in this, our author justly regards the ani- 

 mal kingdom as separating itself into four great types of structure 

 known as Sub-Kingdoms, Provinces, or, as Cuvier originally call- 

 ed them, " Branches.'''' This first distinction is based wholly on 

 the idea of pattern or type. But here the question arises, — type 

 or pattern in what ? In art, when we speak of type, pattern or 

 style, we may refer to a spoon, a piece of calico, or a cathedral. 



„ In nature, in like manner, each great kingdom has its own sets 

 of types, corresponding to the materials employed and the uses 

 they are to serve. If we speak of animals, then, as one portion 

 of the Creator's works, that we may think correctly of their plan, 

 it is necessary that we first clearly comprehend the material and 

 place in nature of the animal, and its truly essential qualities. 



■ This question — what is the animal ? — our author scarcely touches, 

 perhaps because it is so constantly and clearly present to his own 

 mind. We may answer it in its most important bearing by the 

 words used by Linnaeus to indicate the distinction between the 

 animal and the plant, " Sententia, sponteque moventia," adding 

 the related fact, enforced by modern physiology and chemistry, 

 that, in reference to its sustenance and material, the animal life 

 is based upon the vegetable. The animal is an organised being 

 endowed with sensation and volition, and, as the agents of these 

 powers, with nervous matter and muscular fibre ; while to supply 

 the material of these, and maintain their vital powers, it consumes 

 and oxidizes previously organised matter. In other words, the 

 processes necessarily performed by the animal are the assimila- 

 tion and oxidation of vegetable or animal matter. These pro- 

 cesses go on to supply the essential structures of the animal, tele- 



