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And since it is well to study by proceeding from the known to 
the unknown; to make ourselves thoroughly acquainted with 
that which is tolerably familiar to us, so that we may the better 
comprehend that which is new and strange ; let me briefly describe 
the modern Nautilusand its shell, which so much resembles the 
ancient Ammonite. The Nautilus shell is doubtless a familiar 
object to you all, but inall probability you never cut one open to 
examine the interior, perhaps would have rejected the suggestion 
with scorn, as such a mode of acquiring knowledge is supposed to 
be peculiar to children in their treatment of mechanical toys. 
Nevertheless it is a wise proceeding. 
But first of all, let me ask you to look upon this modern Nautilus 
with that respect and reverence which is due to the descendant and 
representative of an old historical family. I remember reading of 
some geologist (I believe it was Murchison, but am not sure), who 
on exhibiting a certain ancient fossil to a friend, said, ‘ Handle it 
reverently ; maybe it is one of the first created things.” I might 
almost say the same of this. Like the Gairfowl on the Allalone- 
stone in Kingsley’s Water Babies it “is of an ancient clan,” and 
might say with that grand old lady, ‘ I am the last of my family.” 
For the Nautilus is found fossilized as low down as the Upper 
Silurian, and some of its close relations lower down still. Those 
who have read geology know what that means. And it has lived 
on eyer since, well nigh unchanged, though the long vicissitudes of 
Time, and now wanders through our seas, solitary and without 
kin. By its aid we shall gain an insight into the nature of our 
Ammonites. 
Well, notice this interior, which one of my students has so care- 
fully cut for me. You would not have expected to find these 
chambers within, so neatly, smoothly, and symmetrically separated 
from each other: There are in this specimen 33 compartments, 
and nothing could exceed the gracefulness of the curves by which 
one is completely isolated from the other. You might almost 
imagine that each cell had been the abode of a separate creature, 
and that the whole shell was a kind of colony or model lodging- 
house. (And let me remark just here that the interior of many 
other shells would surprise you just as much if you examined them ; 
one or two are on the table, though they have no connexion with 
the subject of our lecture). 
Now notice the enormous size of the outer compartment ; in that, 
and in that only the animal lived; the others were simply air- 
chambers which assisted the occupant of the shell in its movements 
through the waters. Of course originally the first compartment 
at the centre of the spiral was the habitation of the nautilus; it 
enlarged its dwelling as its body increased in size; and as it built 
