466 OBSERVATIONS ON THE ANIMALS, &c. 
directed, not to the most promising, but often to the darkest and 
most obscure, points. 
Let not the bearing of this observation upon the subject before us 
be lost sight of. Geology is, and has been for some years, making 
progress with a rapidity and certainty marvellous, and almost incredi- 
ble; but this has been because its votaries have not disdained to 
search in the quarry and the mountain side, in the deep mine 
and the water-course, for the true interpretation of nature. The 
naturalist, the anatomist, the chemist, the mineralogist, all have 
lent their energies to the prosecution of the great work: and 
they have succeeded gloriously. But it is not difficult to foresee 
that if they slacken their efforts—if they leave the examination of 
nature, and resort to theory before the chain of evidence is complete— 
at that moment their steps will become retrogade, and their advance 
change into a retreat. How important, then, is it that every step 
should be sure, every fact, as far as possible, decisive! But since it 
is clear, to every one at all acquainted with the subject, that the re- 
mains of organised matter enter largely into the conditions of every 
geological problem, therefore their study becomes highly import- 
ant, and deeply interesting. 
Now, in all the successive marine deposits, some species of one 
great natural family are invariably met with. This family is the 
Cephalopoda ; and it is of all others the most widely distributed, the 
most numerous, and, what is almost of more consequence than either, 
the most persistent in generic character. Forming as it does the 
connecting link between the vertebrated and invertebrated animals, 
the distinction even of species is, as might have been anticipated, 
more decidedly marked than in any other testacea: and every thing 
seems to point attention to this, as the one class of all others the 
most important to every student as well as teacher of geology. 
If, indeed, zoology is to be brought to bear upon our science, so as 
to multiply facts and increase the value of evidence—if, in consider- 
ing the older and more widely spread formations, the study of organic 
remains is to go hand in hand with mineralogical and lithological 
characters—if we are to judge of contemporaneity of rocks by the 
identity and parallelism of species—then, in all these cases, does it be- 
hove us to study well the whole natural history of the Cephalopoda, 
for in them chiefly, if not entirely, must we expect to find the im- 
portant connecting links, and by their assistance solve the great 
questions at issue. 
