Page:Popular Science Monthly Volume 78.djvu/543

Rh the next ten years ought to see a material advance in our knowledge of the least investigated of the Darwinian principles.

The relative ease with which large numbers of individuals can be secured and observed is an ample explanation of the fact that practically all the studies of selective elimination have been made on invertebrates.

To Dr. H. C. Bumpus belongs the credit of the first effort to determine whether the death rate among vertebrates may depend in some degree upon the measurable physical characteristics of the individual. Indeed, in the attempt to apply quantitative methods to the problem of natural selection Bumpus was a close competitor for priority with Professor Weldon. His statement of the problem, like that of Professor Weldon, is beautifully clear:

From his measurements of various bodily dimensions Professor Bumpus concluded that the birds which perished were actually differentiated from those which survived. Some of the differences, however, are so small that to the cautious statistician this attempt to measure the influence of a selective death rate on the type of a population of birds living in a state of nature seems suggestive rather than finally conclusive.

This must not be read as a criticism of Bumpus's work, for he not only saw the problem and the possibility of applying the new methods to it, but he also gave us the full results from an unusual opportunity.

First and last, considerable has been written concerning natural selection in man. Most of the arguments are purely general or