DEFICIENCY OF TRANSITIONAL FORMS. 149 
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 
