THE GEOLOGICAL MIDDLE AGE. 
179 
ence, and seem to shadow forth by their strange 
contortions the final dissolution of their type. 
When I look upon a collection of these old shells, 
I can never divest myself of an impression that 
the contortions of a death-struggle have been 
made the pattern of living types, and with that 
the whole group has ended. 
Now shall we infer that the compact, closely 
coiled Ammonites of the Jurassic deposits, while 
continuing their own kind, brought forth a vari- 
ety of other kinds, and so distributed these new 
organic elements as to produce a large number 
of distinct genera and species ? I confess that 
these ideas are so contrary to all I have learned 
from Nature in the course of a long life that I 
should be forced to renounce completely the re- 
sults of my studies in Embryology and Palaeontol- 
ogy before I could adopt these new views of the 
origin of species. And while the distinguished 
originator of this theory is entitled to our highest 
respect for his scientific researches, yet it should 
not be forgotten that the most conclusive evidence 
brought forward by him and his adherents is of a 
negative character, drawn from a science in which 
they do not pretend to have made personal inves- 
tigations, that of Geology, while the proofs they 
offer us from their own departments of science, 
those of Zoology and Botany, are derived from 
observations, still very incomplete, upon do- 
