Page:Popular Science Monthly Volume 79.djvu/452

448 the life-processes, those of us who had the misfortune to live and exhaust our greatest enthusiasm during the romantic and morphological periods, can, I suppose, do nothing better with the meager remnant of our vitality than pray for breadth of sympathetic vision on the part of our younger, more numerous and more vigorous contemporaries. The splendid achievements of the investigators who assemble here every summer certainly whet one's desire to see experimental work of the same character accomplished in parasitology. A certain amount of simple experimental work on social parasitism in ants has been inaugurated by Wasmann and myself and continued with interesting results by Santschi, Emery, Viehmeyer, Donisthorpe and others, but more important work, having for its object the artificial production of individual parasites and such studies on the behavior of their descendants as those recently made by Kammerer on the offspring of Amphibia, whose breeding habits had been artificially modified, have not yet been undertaken. Here again, as in so many other cases, the botanists are blazing the trail for the zoologists. The familiarity of the former with grafting, which is merely an artificially induced parasitism, has led them to undertake interesting experiments, like those recently published by Pierce and MacDougal and Cannon. And although these experiments yielded less striking results than might, perhaps, have been expected, they nevertheless emphasize an important fact, which all biologists, except systematists and paleontologists, are too apt to overlook, namely, the extraordinary stability of specialized characters.

Experimental zoologists, including the students of animal behavior, are most keenly interested in the modifiability of the organism, and their experiments are usually devised for the special purpose of determining the amplitude and peculiarities of this modifiability. The entomologist, however, who is attempting to use parasitic insects as tools or implements in controlling the depredations of other insects, is primarily interested in the stability of structure and constancy of behavior. This follows from the very nature of his work. As the essential excellence of a tool consists in its remaining the same as it was when it left the hands of the manufacturer, so a parasitic species can be used as an efficient tool only if it behaves generation after generation with uniform constancy. Hence in combating pests, only those