"T d CAN TONER S V RIO HT 
FROM THE STANDPOINT OF AN IDEALIST. 441 
dispersion. If behind the facts of distribution lies the cardinal principle 
that the farther we trace a type back the more generalized are its characters 
and the wider its range, the question of its original home is obviously not 
raised. 
What, we may ask, was the bearing of these views on general taxonomic 
principles? Bentham was dealing with a world-ranging family holding 
about a tenth of the total known number of Angiosperms and displaying 
relatively few of the difficulties presented by small families with restricted 
distribution. He followed orthodox lines and the results were not dis- 
quieting to the systematist, although, if he had pushed his conclusions home, 
a clash with prevailing practice would have happened. With Huxley it 
was very different, He was concerned with a much smaller family, one 
less widely distributed and displaying a preference for mountainous regions. 
To it he applied the same method of postulating a wide-ranging but little 
differentiated primitive type, and in so doing he raised many of the difficulties 
presented by the smaller families. But his method, as he perceived, con- 
siderably upset the accepted grouping of the Gentians, and in his enthusiasm 
in its advocacy he contended that “a revision of Taxonomy and Distribution 
from the point of view of the Evolution doctrine will hardly fail to revolu- 
tionise both.” But the curious point is that as far as the early stages in the 
history of the Gentians are concerned the method advocated by Huxley was 
not Darwinism, as then conceived. It was pure Differentiation. With 
Bentham also, although clinging to the idea of a centre of dispersion, or of 
a home, for the Composite, he began with a world-ranging but slightly 
differentiated primitive type, and like Huxley with the Gentians he allowed 
it to work out its own lines of differentiation in the various regions of the 
globe. This is Evolution on a plane; and the implication is that since the 
rise of the great families in the Mesozoic ages little else has been effected. 
The Differentiation hypothesis —Although this hypothesis has rarely been 
formulated, there are various ways of stating it. It appears in a variety of 
guises in many a monograph of the families. The writer’s mode of pre- 
senting it is to associate it with another theory relating to the differentiation 
of conditions, the modification of form being regarded as the response to the 
progressive differentiation of conditions. But it would be possible to deal 
independently with the différentiation through the ages of the family into 
tribes, of the tribe into genera, and of the genus into species. Yet the two 
are commonly implied, and it is hard to dissociate the idea of differentiation 
of type from that of diversification of condition. There may, however, be 
different ways of stating the relation. The following is the writer’s method 
of doing so. 
He has come to close quarters with the central problem in successive 
stages. In the first stage the world, as far as plants are concerned, was 
mainly a differentiating world in which wide-ranging generalized types had 
