110 THE CONDOR Vol. XXIV 
means to fit as a shoe to a foot or a key to a lock. But, so far as one can see, 
no such idea and word to express it, would ever have arisen if everything fitted 
absolutely. If we are to have any real idea of adaptiveness or fitness, we must 
apply the good, better, best criterion to it. Otherwise expressed, the idea of fit- 
ness is composed of these degrees. 
Now so obvious is this, once one thinks over the matter a little, that it is 
surprising to find how frequently thought and expression ignore partly or whol- 
ly this gradation in its excellence, even when speaking of adaptation. The ignor- 
ing is particularly apt to occur in theoretic discussions of evolution and natural 
selection. One hears repeatedly that an individual or species is adapted, or is 
not adapted, and consequently survives or does not survive. The idea of being 
more or less well adapted, and hence of surviving more or less well, comes far less 
definitely into thought than into the actual processes of nature. This diserep- 
ancy in our conceptions is largely due no doubt to the great difficulty of getting 
exact quantitative information in any given instance as to how much departure 
there is from perfect adaptation; as to how much falling short of complete sur- 
vival there is; and as to the rate at which improvement is made. And the diffi- 
culty of getting such information is clearly due in large part to the exceeding 
complexity of evolutionary phenomena and the slowness with which, generally 
speaking, they go on. 
Try to imagine, even in an approximately statistical way, the main changes 
involved in the evolution of such a relatively simple thing as the pelican’s scoop- 
net, and see where you come out. Notice that you have only some hypothet- 
qualitative data, to say nothing about exact quantitative data, even to make a 
start with. But suppose yourself satisfactorily started, from, say, a slightly de- 
veloped gular pouch like that of the cormorant: What next? What exactly 
measured structures and functions between the slightly developed cormorant 
stage and the highly developed pelican stage is there in your imaginary sta- 
tistics ? ) 
We must come to the main point of this little preliminary. 
I take it for granted that no naturalist, especially no field ornithologist, 
doubts for a moment that the activities of animals are quite as subject to the 
principle of adaptation as are any of their structures. This being granted what 
IT want to say in a nutshell is that the problem of adaptation in animal activi- 
ties, particularly in animals of median rank, as for example in many insects, 
many birds, and many mammals, is, I believe, amenable at certain points to much 
more satisfactory attack by scientific research than it is in connection with ani- 
mal structures. This is so because many activities adapt themselves much more 
quickly and widely than do the vast majority of structures. 
A familiar ease will make the meaning clear. Take the enormous variety 
of activities of which the human hand is capable. Think of the difference both 
as to the action itself and as to the results. between the hand work of a skilled 
pianist and a skilled watch repairer! Yet the structural difference in the hands 
in the two eases is very slight, relatively. | 
_ But would any one question that great numbers of hand activities are as 
truly adaptive as were the structural changes involved in the production of the 
hand originally? And almost any organ of almost any animal shows something - 
of this lack of close coincidence between structural and functional adaptation. 
Indeed, so much more responsive to changed conditions, so much more pliable, so 
