171 



through using the metaphors which I selected for the 

 elucidation of a principle, it be supposed that I would 

 wish them to apply to the smaller details, likewise, of 

 the problem. If a genus has been portrayed under the 

 similitude of a bulb, or of a nodule (formed by the ap- 

 proximation of beads which more or less resemble each 

 other in their primary aspect), it does not follow that 

 either bulb or nodule are to diminish in a similar ratio 

 towards their respective circumferences, or, which is the 

 same thing, that they are to be symmetrical ; whether 

 spherical, ovoid, or otherwise. The general method of 

 the organic creation is a progressive one; and its suc- 

 cessive types, therefore, will not always be found to 

 radiate equally from their normal foci : so that it is in the 

 direction of the higher (rather than the lower) extre- 

 mities of the assemblages that those foci are usually to 

 be discerned ; and where the groups are large, it is not 

 often difficult to pronounce which of their ends are, as a 

 whole, the more perfectly developed. 



It will, moreover, be further acknowledged (if my 

 premises are allowed), that, since it is a somewhat 

 central position which the typical member of a genus 

 usually occupies, the diagnostic characters, although (in 

 combination) carried out to the full, are more evenly 

 balanced in a generic type than in any of its associates ; 

 or, in other words, that a species in which any single 

 organ is monstrously enlarged, at the expense of the 

 rest, is seldom typical of the assemblage with which it is 

 placed ; but may be a priori regarded as in all proba- 



