THE POPULAR SCIENCE MONTHLY.
to him; it were easier to explain a shadow to the sun, who always sees the lighted side. To state the whole epigrammatically, German science is the professional investigation of detail, slowly attaining generalization.
The Law of Heredity. A Study of the Cause of Variation, and the Origin of Living Organisms. By W. K. Brooks, Associate in Biology, Johns Hopkins University. Baltimore: John Murphy & Co. Pp. 336.
This work combines in a very unusual degree the two traits that are so rarely found to coexist in scientific books: it is both original and independent in its views and is at the same time a most lucid and popular presentation of its subject. While the work is as far as possible from being a compilation, and will be sure to take its place as a valuable contribution to philosophic biology, the author has, nevertheless, given us such a survey of the general subject as will prove interesting and instructive to all readers. We needed a good exposition of the nature and present condition of the fundamental problems of heredity, and we here have it by one who has labored systematically and effectively in the direction of their solution; and what is perhaps still more to the purpose, we have it in the light of a new and advanced theory of the subject of extreme interest, and which will probably prove a permanent and valuable contribution to the inquiry.
Dr. Brooks devotes his first chapter to the question, "What is heredity?"—and he gives his readers a vivid idea of the marvels which it involves. Of course, people who have no real or accurate knowledge on the subject of life are but ill prepared to appreciate its subtilties, and our author observes that such people are apt to "regard an adult animal with feelings similar to those with which an intelligent savage might regard a telephone or a steamboat. ... A dog with all the powers and faculties which enable him to fill his place as man's companion is a wonder almost beyond our powers of expression; but we find in his body the machinery of muscles and brains, digestive, respiratory, and circulatory organs, eyes, ears, etc., which adapts him to his place; and study has taught us enough about the action of this machinery to assure us that greater knowledge would show us in the structure of the dog an explanation of all that fits the dog for this life—an explanation as satisfactory as that which a savage might reach in the case of the steamboat by studying its anatomy.... Let our savage find, however, while studying an iron steamboat, that small masses of iron without structure, so far as the means at his command allow him to examine and decide, are from time to time broken off and thrown overboard, and that each of these contains in itself the power to build up all the machinery and appliances of a perfect steamboat. The wonderful thing now is, not the adaptation of wonderful machinery to produce wonderful results, but the production of wonderful results without any discoverable mechanism; and this is, in outline, the problem which is brought before the mind of the naturalist by the word heredity.... In the mind of the naturalist the word calls up the greatest of all the wonders of the material universe: the existence in a simple, unorganized egg, of a power to produce a definite adult animal with all its characteristics, even down to the slightest accidental peculiarity of its parents—a power to reproduce in it all their habits and instincts, and even the slightest trick of speech or action."
Dr. Brooks then proceeds to state various other striking and subtile phenomena involved in heredity, and then intimates that, notwithstanding their refinement and obscurity, they are unquestionably capable of being cleared up so as to be as fully understood as other scientific laws. He says: "We may not be able as yet to penetrate its secrets to their utmost depths, but I hope to show that observation and reflection do enable us to discover some of the laws upon which heredity depends, and do furnish us with at least a partial solution of the problem; that we have every reason to hope that in time its hidden causes will all be made clear, and that its only mystery is that which it shares with all the phenomena of the universe."
Chapter II, on the "History of the Theory of Heredity," is of extreme interest. He traces the most notable speculations upon the subject that have been made in past times, and points out their inadequacy