290 



Design, on what the theologians of the last century were wont to lay the 

 greatest stress. As we have just seen, there are two ways in which the 

 human mind strives to represent to itself the divine activity in the universe of 

 matter. According to the one mode of thought, the general plan of Creation 

 is paramount ; according to the other, the particular creatures. Corresponding 

 with this division is the difference between the past and present aspects of 

 Organic science. The naturalist of last century separately examined each par- 

 ticular species of the Animal Kingdom, with reference to its external form, and 

 mode of life. Great stress was laid in classification upon such characters, as 

 the nature of food ; whether it were a carnivorous, • herbivorous, or insec- 

 tivorous creature : or the habitat whether terrestrial, aerial, or aquatic ; or the 

 mode of progression, whether on hoofs, by wings, by fins or otherwise ; in 

 short, upon which it seemed fitted to attain. 



This method of classification is known as Teleological, or purposive, (from 

 " telos " an end, a purpose) being based on the apparent purpose of an organism 

 rather than on its structure, or course of development. But there are radical 

 objections to this method of arrangement. "It is frequently found that two 

 organs which are not unlike in external form, and which have corresponding 

 functions in the system, originate from elements entirely different, and ai^e 

 therefore fundamentally dissimilar ; while, and on the other hand, organs which 

 at first sight present little or no resemblance to each other, and are applied to 

 very different purposes in the economy, may be really modifications of the 

 same fundamental component." — Carp. § 4. 



The wings of Insects, as compared with those of Birds, are a good instance 

 of the identity of function combined with fundamental diversity of structure. 

 In structure the wings of Insects really are analogous, or, as the phrase now is, 

 homologous, with certain structures, which in other articulated animals 

 constitute part of the breathing apparatus. Hence Oken calls the wings of 

 Insects '■' aerial gills." The attempt to bring into comparison the wings of 

 insects with those of birds and bats can now, as Carpenter observes, only 

 excite a smile on the part of the philosophical anatomist. Again, the gills of 

 fishes coriespond in function with the lungs of air-breathing vertebrates. 

 But, in structure, lungs are the homologues, not of the gills, but of the air- 

 bladder in Fishes ; an organ which has no respiratory function. Modern 

 classification no longer proceeds, therefore, upon analog]/, that is resemblance 

 of function, but upon homology, that is identity, of structural type. With the 

 modern naturalist, the question is, not, what life the animal was meant to lead, 

 but, what is the formal plan on which it is constructed 1 Proceeding thus, he 

 finds, "that in the several tribes of organised beings, we have, not a mere 

 aggregation of individuals, each formed upon an independent model, and 

 presenting a type of structure peculiar to itself, but that we may trace through- 

 out each assemblage, a conformity to a general plan which may be expressed 

 in an 'archetype,' or ideal model.*" * * * " The typical 



structure of any group being given, the different habits of its component 

 species, or minor groups, are provided for, not by the creation of new organs, 

 or the destruction of others, but by the modification in form, structure, or 

 place, of organs typically belonging to the group. t This method in natural 

 science is known as the Morphological (from " morphe "), " form ;" because it 

 regards community of form or type. The obvious defects in the arrangement 

 of the mammalia, by the illustrious Cuvier, seems attributable to his partial 

 adherence to the teleological method. His great primary division into 

 Unguiculata (clawed), Ungulata (hoofed), and Mutilata (wanting the posterior 



* Carpenter, " Comp. Physiol.," § 11. 

 t Ibid,'% 77, (citing Bell on " British Crustacea.") 



