266 A Review of the Modern Doctrine of Evolution. . [ April, 
preceded. It seems that evolution has witnessed a continual run- 
ning down of types to their great specialization or extinction. 
That many types have arisen in weak and small beginnings, but 
that the conflict with more powerful forms has developed some 
qualities in which they sooner or later excelled, and which formed 
the basis of their future superiority and persistence. That while 
this has probably been the true cause of the origin of the many 
admirable mechanical adaptations displayed by animals, it is pre- 
eminently true of the development of mind. That the reason 
why progress has reached its limit in the lines of greatest spe- 
cialization, has probably been the removal of the occasion of its 
original cause, 2. e., active exercise in the struggle for existence. 
This explanation is suggested by the remarkable degradation 
which is witnessed in animals whose mode of life’ relieves them 
from the nécessity of working for a livelihood, e. g., the parasites 
and sessile animals whose young are free. Some of these crea- 
tures, on assuming their parasitic life, lose the semblance of even 
the order to which their young belong. The primary stages of 
various plants move actively through the water like the lowest 
forms of animals, and their sessile adult condition must be-looked 
upon as a degeneration. It is well known that the endeavor to 
relegate the lowest forms of life to the two kingdoms of animal 
and vegetable, has been generally abandoned. The great vegeta- 
ble kingdom probably exhibits a life degraded from more animal- 
like beginnings. Animal irritability and mobility have been lost, 
and their own consciousness must be entirely eliminated from the 
question of the origin of the many later and specialized types of 
plants. But I venture here the hypothesis that the consciousness 
of plant-using animals, as insects, has played a most important 
part in modifying the structure of the organs of fructification in 
the vegetable kingdom. Certain it is that insects have been 
effective agents in the préservation of certain forms of plants. I 
would suggest whether the mutilations and strains they have for 
long periods inflicted on the flowering organs, may not, as in 
some similar cases in the animal aati have originated pecu- 
liarities of structure. 
Evolution of living types is then a succession of elevations of 
platforms on which succeeding ones have built. The history of 
one horizon of life is, that its own completion but prepares the — T 
way of a higher one, furnishing the latter with conditions of &- 
