114 
MONOGRAPH OF THE GENUS STROPHIA. 
of life. First, it loses its color, then the shell grows thinner and 
lighter, but in order that the animal may grasp it more firmly and 
prevent its being blown away during the prevalent tempests which 
occur, when the Strophia must be actively moving about, in August 
and September, for there is considerable rainfall in both these months 
and mollusks of this genus move in damp weather, a tooth is developed, 
which is not usually found in the ancestor, S. curtissii, namely the 
upper, and the aperture is narrowed and its margin pushed forward. 
These are apparently slight alterations, but they mean much to this 
small animal, and are as comparatively important to it as more easily 
seen changes in other and larger animals. We have seen how the 
form of Strophia curtissii living on Spotter’s Key has altered its shell 
to suit its new home. Now who can say but what the animal within 
the shell has not changed also. At all events, an important portion of 
the animal has changed. Now, when I maintain that such changes 
after becoming fixed, as in time they do become fixed, as we find they 
do in many cases in this genus, constitute good and sufficient specific 
characters, I may be indulging in the rankest kind of conchological 
heresy ; but is not such heresy, when, guided by facts, I apply the 
truths of evolution, in which every thinking naturalist believes, practi- 
cally, in the naming of species, better, as indicating progression in the 
right direction, than conservatism, which means stagnation? I simply 
trace the changes which those animal are undergoing and, believing as 
I do, that all animals have halting places in the great system of 
changes, I endeavor to indicate these halting places by imposing a 
name upon the animal, which, assuming certain characters, has become 
quiescent as a form, for a time. 
I once again repeat, what I have had occasion to state many times, 
and be it remarked I speak from a long and extended experience, that 
the genus Strophia is exceedingly plastic, evolving species much more 
readily than many genera of shells. The species are exceedingly local 
in distribution, and slight causes isolate colonies, that when so isolated 
speedily assume characters consistent with their environment, and 
these characters I consider, as I am forced to do, looking at the whole 
matter broadly and consistently, as specific. In my account of the 
genus Strophia I have been very careful not to overstate anything, nor 
have I formed any theories unsupported by facts, and as far as I have 
gone I have not taken any steps which I wish to retrace. 
I feel constrained to make these and similar remarks, inasmuch as 
I know that I am looking upon the matter which I have in hand, from a 
