4i 6 



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. 



LITERARY NOTICES. 



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 philo- 

 sophic biology, the author has, nevertheless, 

 given us such a survey of the general sub- 

 ject as will prove interesting and instructive 

 to all readers. We needed a good expo- 

 sition 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 direc- 

 tion 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, peo- 

 ple who have no real or accurate knowl- 

 edge on the subject of life arc but ill pre- 

 pared to appreciate its subtilties, and our 

 author observes that such people are apt 

 to " regard an adult animal with feel- 

 ings similar to those with which an in- 

 telligent 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 knowl- 

 edge 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 anat- 

 omy. . . . 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 wonder- 

 ful 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 ani- 

 mal 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 va- 

 rious 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 un- 

 derstood 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 6how that observation and reflec- 

 tion 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 phe- 

 nomena of the universe." 



Chapter II, on the " History of the The- 

 ory 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 



