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THE POPULAR SCIENCE MONTHLY. 



importance to the causes of variation than 

 to any of the other problems considered by 

 Darwin, among which functional activity and 

 external conditions seemed the most pow- 

 erful. He was thus led to believe that a 

 deeper insight into the phenomena of evo- 

 lution would ultimately be obtained by pur- 

 suing the line of inquiry suggested by La- 

 marck, than by continually searching for 

 new instances of adaptation to be explained 

 by the Darwinian formula. While in this 

 frame of mind he was u delighted to find " 

 that Weismann had to contend with a for- 

 midable opponent in his own country, and 

 concluded that he could not for the present 

 oppose the progress of his views more effect- 

 ively in England than by publishing a trans- 

 lation of Prof. Eimer's arguments. It had 

 seemed to this author long ago to be of the 

 greatest importance to undertake an investi- 

 gation of the question whether the modifica- 

 tion or variation of the species of animals is 

 not governed by definite laws. The Darwin- 

 ian theory suggested none. The investiga- 

 tion of the laws of variation included the 

 question of the causes of variation. There 

 was likewise a gap in the Darwinian theory 

 where these should be explained. The prin- 

 ciple of utility, the selection of the useful in 

 the struggle for existence, did not explain 

 the first origin of new characters, but only, 

 and that partially, the progress and the 

 gradually effected pre-eminence of those 

 characters. If we could know, the author 

 assumed, all the natural laws which have 

 operated in the evolution, and which operate 

 in the existence of a single animal or a sin- 

 gle plant, we should understand the laws of 

 the organic world altogether. Applying this 

 principle, the unreserved study of a single 

 species of animal, the author declares, led 

 him to the discovery of a whole series of 

 laws, which the extension of the investiga- 

 tion to other species showed to hold good 

 generally. This animal was the wall-lizard 

 (Lacerta muralis ccerxdea), a species of re- 

 markable variability, with which he became 

 acquainted on the rocks of Capri. The re- 

 sult of his researches, which were extended 

 to various classes of animals, "was the recog- 

 nition of the dominion of laws in the process 

 of variation, not only of the lizard, but also 

 in the most diverse tribes of the animal 

 kingdom ; these laws holding firstly in the 



variations of marking, previously regarded as 

 quite indifferent, unimportant, or fortuitous, 

 but also applying to other characters. I was 

 able to demonstrate that variation every- 

 where takes place in quite definite direc- 

 tions which are few in number, and I was 

 able on the basis of my observations to put 

 forward the view that the causes which lead 

 to the formation of new characters in or- 

 ganisms, and in the last result to their evo- 

 lution, consist essentially in the chemico- 

 physiological interaction between the mate- 

 rial composition of the body and external 

 influences. Finally, I succeeded, through the 

 facts I established, in referring the separa- 

 tion into species, ... in connection with 

 the rest of my views, to natural causes." 

 Previously to presenting these results in the 

 present volume, a brief review is given of 

 the newest theories concerning evolution. 

 The translator has endeavored to make his 

 work sufficiently English to be readable, and 

 to preserve the full force and exact signifi- 

 cance of Prof. Eimer's expression. 



A Short Course of Experiments in Physi- 

 cal Measurement. By Harold Whiting. 

 In Four Parts. Part I: Density, Heat, 

 Light, and Sound. Cambridge: John 

 Wilson & Son. Pp. 278. 



The course of laboratory work which this 

 book is to comprise covers the ground of 

 both the " minimum " and the " maximum " 

 requirements in physics for admission to 

 Harvard College, and it is intended also to 

 serve as a preparation for courses in me- 

 chanical and electrical engineering in other 

 institutions. Mental training is the chief 

 object aimed at, through the care required, 

 and the practice in inductive and controlled 

 methods secured. The policy of the book is 

 rather " to show how comparatively accurate 

 results may be obtained by rough apparatus, 

 than to explain the use of instruments of 

 precision, which in the hands of a student 

 are apt to give erroneous results." The au- 

 thor states that not so much mathematics is 

 involved in these experiments as would ap- 

 pear from a first glance, because many proofs 

 are given in full here which in most text- 

 books have been taken for granted. The 

 volume is illustrated with many cuts of ap- 

 paratus. The second, third, and fourth parts 

 are to contain experiments in other depart- 

 ments of physics. 



