462 THE CAUSES OF THE XI 
pigeons, for example; you have the dove-cot 
pigeon, which closely resembles the rock pigeon, 
from which they all started, existing at the same 
time with the others. And if species are developed 
in the same way in nature, a primitive stock and 
its modifications may, occasionally, all find the 
conditions fitted for their existence; and though 
they come into competition, to a certain extent, 
with one another, the derivative species may not 
necessarily extirpate the primitive one, or vice 
versa. 
Now palzontology shows us many facts which 
are perfectly harmonious with these observed 
effects of the process by which Mr. Darwin sup- 
poses species to have originated, but which appear 
to me to be totally inconsistent with any other 
hypothesis which has been proposed. There are 
some groups of animals and plants, in the fossil 
world, which have been said to belong to “ persist- 
ent types,’ because they have persisted, with 
very little change indeed, through a very great 
range of time, while everything about them has — 
changed largely. There are families of fishes 
whose type of construction has persisted all the 
way from the carboniferous strata right up to the 
cretaceous ; and others which have lasted through 
almost the whole range of the secondary rocks, 
and from the lias to the older tertiaries. It is 
something stupendous this—to consider a genus 
lasting without essential modifications through all 
