SPECULATIVE CAUTION 497 
Happily this resolve was broken by the impulse of 
Darwin's compulsory publication. 
However, Hooker's long established conviction that species 
are more variable and less easily defined than most naturalists 
believed, did not bring him at once into the Transmutationist 
camp. He accepted the considerable variability of species 
and their spread by migration each from some one original 
starting place, a point less difficult perhaps to define than the 
perplexing modes of migration : he accepted even their relation- 
ship to allied species, their fossil predecessors in the same area, 
but to accept so much was not to accept their transmutation 
from other species. He went to India * possessed, but not 
converted ' by Darwin's theories, and was somewhat dis- 
appointed not to find them cleared up by the discovery of 
transitional forms in Sikkim, the meeting ground of tropical 
and arctic flora. The actual process of transition had not been 
observed ; the partial light thrown on the question in frag- 
mentary discussions was not enough, and until 1858-9, after 
the consolidation of Darwin's arguments in the famous Abstract, 
Hooker, as has been already noticed, worked avowedly on the 
accepted lines of the fixity of species, for which he had so far 
found no convincing substitute. 
His critical attitude so long maintained may be regarded 
less as opposition to the tendencies of Darwin's speculations, 
than as the caution of a judicial mind, that required wholly 
convincing proof for itself before accepting the theory 
and all its consequences, and was equally desirous that the 
proof be wholly convincing for the credit of the friend who 
advanced it. Darwin never tires of telling how he values his 
criticisms. They led not to destruction, but to reconstruction. 
* You never make an objection without doing much good,* 
he exclaims (November 18, 1856). After a long talk together, 
* fighting a battle with you clears my mind wonderfully ' 
(October 19, 1856), or, touching Hooker's help over the question 
of large genera varying largely, already mentioned, * Again 
I thank you for your valuable assistance. . . . Adios, you 
terrible worrier of poor theorists ! ' 
But as long as the full argument of the ' Origin ' had not 
