DEFICIENCY OF TRANSITIONAL FORMS. I49 



are periods of relative disturbance. During their con- 

 tinuance the exigency of adaptation and transformation 

 was at its height, both in the vegetal and animal world ; 

 the conditions of existence at the same time most 

 unfavourable ; the number of individuals in those species 

 which succeed in effecting their transformation is neces- 

 sarily reduced, and could increase again only in the 

 subsequent periods of repose. It is therefore not sur- 

 prising that the catalogue of intermediate forms is so 

 defective ; and their scarcity is remarked upon only by 

 those who are determined to feel the want of them. For 

 the establishment of scientific evidence in favour of the 

 doctrine of Descent we have them in superabundance. 



With the supposed deficiency of transitional forms is 

 connected another frequent objection, namely, that in 

 repeated instances whole groups of kindred species have 

 suddenly appeared. If intermediate morphological and 

 anatomical gradations are elsewhere visible, in these 

 groups, the pterodactyls, birds and others, there is no 

 coherence and connection with any aboriginal species 

 previously or contemporaneously existing. This allega- 

 tion is one of the feeblest and most vapid, if raised 

 after the attempt has been made to account for the 

 absence of intermediate forms. It is only a particular 

 case in the alternative that either all species originated in 

 the natural manner indicated by the perfectly adequate 

 number of transitional forms at hand, or all by miracle 

 In the cases which are here brought forward as heavy 

 artillery, the gap to the aboriginal species is certainly 

 greater than where there is merely a leap from species 

 to species or to genus. But the explanation given of 

 the less striking intervals scarcely needs extension to 



