December 24, 1915] 



SCIENCE 



911 



Gorgas, Dr. Holmes and Dr. Woodward have 

 been added to the executive committee. The 

 conilict in time does not extend to the second 

 week of the Pan-American Congress, and it is 

 probable that after the adjournment of the 

 Columbus meeting a special meeting of the 

 American Association will be held at Wash- 

 ington. Under existing conditions, it is ex- 

 tremely desirable that friendly relations and 

 cooperation in science should be maintained 

 among the American republics. — The Scien- 

 tific Monthly. 



SCIENTIFIC BOOKS 

 Elemente der exalden Erhlichheit mit Grund- 



zugen der iiologischen Variationssiatistik. 



By W. JoHANNSEN. Zweite deutsche, neue 



bearbeitet und sehr erweiterte Ausgabe. 



Jena, G. Fischer. 1913. 724 pp.; 35 figs, in 



text. 



The second edition of Johannsen's epoch-ma- 

 king work which follows the first by only four 

 years has added nearly 200 pages, or 40 per 

 cent., to the first edition. The number of lec- 

 tures has been increased from 25 to 30, by 

 the division of one to which much material has 

 been added, by wholly new lectures (Nos. 

 12, 13) and by five final lectures instead of 

 three. 



The significance of Johannsen's book can 

 now, after the lapse of years, be better evalu- 

 ated than before. It had long been a truism 

 in biology that the hereditary substance — ^the 

 stirp or germ — must be carefully distinguished 

 from the person or soma, and Galton was one 

 of the earliest to make this distinction. It was, 

 therefore, a great step backward when Galton 

 announced his law of ancestral heredity ac- 

 cording to which an individual inherits from 

 his two parents together 50 per cent, of his 

 whole heritage; from his four grandparents 

 25 per cent., and so on. It only testifies to 

 the depth of the darkness in which we were 

 groping that any of us should have seized upon 

 that as a solution of the mystery of heredity. 



The rediscovery of Mendel's law wiped away 

 that fog and brought us again to germ cells. 

 Still we did not fully sense the bearings of 

 that law. We still clung fondly to the idea 



that the soma was so important an index to the 

 hidden germ plasm that we could make prog- 

 ress by somatic selection. And it required the 

 first edition of Johannsen's " Elemente " to 

 set us straight there. Ever since we have 

 recognized that even if one can make progress 

 by somatic selection it is more or less by acci- 

 dent and by rule-of-thvunb. For what we are 

 selecting is truly the germ plasm, even though 

 we think we are selecting somas; and we are 

 successful only in those cases in which there 

 happens to be a considerable correlation be- 

 tween the two. Ever since Johannsen's book 

 appeared somatic selection merely — as such — 

 has been realized to be futile for evolution, 

 although somatic selection as a means of 

 eliminating or preserving certain kinds of 

 germ plasm may be, and in some cases is, of 

 great theoretical and practical importance. 



In the new edition, new, original experi- 

 mental material on pure lines in beans is af- 

 forded with results quite the same as before. 

 More space is given to a critical examination 

 of the later studies on selection such as the 

 favorable ones of Jennings, East, Pearl, Tower 

 and Gates and the unfavorable ones of Castle, 

 Lutz and Harris among American investi- 

 gators. The unfavorable investigators Jo- 

 hannsen finds to fall into two groups; those 

 whose experiments have yielded results op- 

 posed to Johannsen's and those who, without 

 contradicting his results, have opposed their 

 general validity. The opposing experiments 

 rest either on the fact that the original mate- 

 rial was not homogeneous or result from a 

 " secondary selection " such as the selection 

 of the best nourished individuals whose young 

 start life in each generation on a higher nutri- 

 tion-plane even though no genotypic change 

 has occurred. There seems to the reviewer a 

 certain weakness in the author's explanation 

 of the discordant results of some workers 

 (e. g., Lutz). It would seem more probable 

 that some of the favorable results of selection 

 are due to unexpectedly abundant mutation. 

 The last 90 pages of the book contain the 

 most new material. Here are recorded, with 

 evidence of great research into the literature, 

 the results of the newer experiments in hered- 



