26 
I labor under the double disadvantage of having prepared there- 
for no specimens, having brought before you nothing to make my 
theme comprehensive, and also the final disadvantage of having no 
blackboard ; but I will do the best I can to make my point com- 
prehensible. 
The subject which I proposed to present to the Society is what I 
should call the ‘‘ Phylogeny of an Acquired Characteristic,’’ the his- 
tory of one single characteristic followed out from its earliest inception 
in the type of cephalopods through various stages of its evolution to 
its final disappearance in the same type. The object is to give asolid 
basis to certain theories of evolution. 
You all, of course, know that in the present treatment of the 
problem of evolution everything depends on having some specific 
object. It is well enough to speculate, it is well enough to state 
the Darwinian hypothesis, it is well enough to have this hypothesis 
or that point of view and to argue about them, but to come down 
to the facts which lie at the bottom of these, and to follow them 
through all the phases of their evolution is, of course, difficult and 
largely a matter of chance in every department of research. 
In this case, one characteristic happens to be provable, and fur- 
nishes the subject which I have in hand for special investigation. 
The earliest shells, those which are primitive in shape, are cones 
like this. (lIllustrating.) They are divided by partitions and have 
certain internal characteristics which distinguish them. The next 
shape is bent, as if I were to take this cone and bend it without 
crushing in one side. The next form is loosely coiled, as if I 
doubled this paper cone without depressing one side, the cone not 
coming in contact. The next stage of evolution is one in which 
the cone not only doubles on itself by growth, but doubles so closely 
that it actually flattens this inner side, and then, in place of being 
able to see these inside convolutions in the next state of evolution, 
they are concealed by the downward growth of the outside. So 
that the shell, growing gradually, first like a rope coiled up, and 
then eventually, if you can imagine the sides of the coil growing 
inwards as they progress, so as to cover up the interior, you would 
see the last or outside convolution with a depression like that (illus- 
trating) in a horseshoe shape, on the inner side. These whorls, the 
first of them: in the Devonian and Silurian period, are always 
rounded, so that the section is very much like a section of the end 
of that cone, it has no depression on the inside. ‘Then, as the 
