CURRENT LITERATURE 



BOOK REVIEWS 



Inbreeding and outbreeding 



The latest of the series of "Monographs on Experimental Biology" is by 

 East and Jones. 1 The book is noteworthy in bringing together in conven- 

 ient form critical data on an important subject, which have heretofore been 

 neither well organized nor readily accessible. Some will object to certain 

 conclusions, but they enhance the value of the book as a monograph, and all 

 assertions are supported by striking evidence. 



Chapter i describes the nature of the problem, discusses its sociological, 

 agricultural, and evolutionary significance, and emphasizes the necessity of 

 proper experiments for its solution. Chapter ii outlines briefly the position 

 of cross-fertilization in the evolution of reproduction in plants and animals. 

 The conclusion is that those organisms which were able to cross with others, 

 at least occasionally, have dominated the organic world. For Darwin's 

 negative proposition, "Nature abhors perpetual self-fertilization," a positive 

 substitute is provided in, "Nature discovered a great advantage in an occa- 

 sional cross-fertilization." 



Chapter iii is a very condensed description of the role and behavior of 

 chromosomes in plant and animal reproduction. Sex determination and sex 

 linked inheritance are also included, although the reviewer doubts whether 

 these are necessary. Chapter iv presents Mendel's law, wisely using a 

 1:2:1 ratio as the type illustration, linkage, and the factor hypothesis, with 

 particular emphasis on the inheritance of quantitative characters. The role 

 of the factor as a mathematical concept, similar to the chemical atom, is ably 

 presented. Chapter v discusses mathematically the effect of various types of 

 inbreeding upon the heterozygosity of a population. Chapter vi presents 

 the inbreeding experiments of Crampe, Ritzema-Bos, Weismann, von 

 Guaita, King, Rommel, Castle, Whitney, and A. F. Shull on animals, 

 and of Darwin, G. H. Shull, and of the authors themselves on plants. The 

 emphatic conclusion is that inbreeding is not injurious merely by reason of 

 the consanguinity; apparent evil results are due merely to the isolation of 

 certain recessives. 



Chapter vii describes the experiments of Kolreuter, Knight, Gart- 

 ner, Naudin, Mendel, Focke, Darwin, East and Hayes, Roberts, Col- 

 lins and Kempton, Gernert, and Sargeret on hybrid vigor in plants. 



1 East, E. M., and Jones, D. F., Inbreeding and outbreeding. 8vo. pp. 285. 

 figs. 46. Philadelphia: J. B. Lippincott Co. 1919. $2.50. 



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