82 PHYSIOLOGY OF LIFE. 



First, that in the lower grade the reproductions themselves 

 seem merged in those of irritability, from the very circum- 

 stance that the latter constitutes no pole, either to the 

 former, or to sensibility. The force of irritability acts, 

 therefore, in the insect world, in full predominance ; while 

 the emergence of sensibility in the fish calls forth the op- 

 posite pole of reproduction, as a distinct power, and causes 

 therefore the irritability to flow, in part, into the power of 

 reproduction. The second result of this ascent is the 

 direction of the organizing power, ad intra, with the con- 

 sequent greater simplicity of the exterior form, and the 

 substitution of condensed and flexible force, with compara- 

 tive unity of implements, for that variety of tools, almost 

 as numerous as the several objects to which they are to 

 be applied, which arises from, and characterises, the super- 

 ficial life of the insect creation. This grade of ascension, 

 however, like the former, is accompanied by an apparent 

 retrograde movement. For from this very accession of 

 vital intensity we must account for the absence in the 

 fishes of all the formative, or rather (if our language will 

 permit it) fabricative instincts. How could it be otherwise ? 

 These instincts are the surplus and projection of the or- 

 ganizing power in the direction ad extra, and could not, 

 therefore, have been expected in the class of animals that 

 represent the first intuitive effort of organization, and are 

 themselves the product of its first movement in the direc- 

 tion ad intra. But Nature never loses what she has once 

 learnt, though in the acquirement of each new power she 

 intermits, or performs less energetically, the act imme- 

 diately preceding. She often drops a faculty, but never 

 fails to pick it up again. She may seem forgetful and 



