September 3, 1915] 



SCIENCE 



313 



of course, be readily conceded as an article of 

 broadmindedness ; meanwhile we must wait 

 for a specific case where it can be shown that 

 males and females may be turned out in these 

 different ways. For, while no one doubts that 

 such things as blue flowers, let us say, may be 

 due to different pigments that go back in 

 origin to different factors, yet so far as known 

 to the reviewer there is no case in the whole 

 Mendelian literature where it has been proved 

 that the same (not merely similar) product is 

 the result of different factors. 



A somewhat similar question comes up in 

 connection with certain attempts that have 

 been made to account for departures in the 

 sex ratio on the basis that the sex factor has 

 become " weakened." The result would lead 

 to complete mix-up of the chromosome rela- 

 tions and would lead to chaos in subsequent 

 generations if the same kind of " weakness " 

 kept up. In contrast to such speculations the 

 relative constancy of the chromosome number 

 must appear an impressive fact. Doncaster 

 himself, while lending a sympathetic ear to 

 those who find difficulties in applying the 

 chromosome interpretation to sex determina- 

 tion, takes in general the stand with which 

 most of us will heartily agree, namely, to 

 hold fast to what has been most clearly demon- 

 strated and not let the fact that there are 

 still unsolved problems confuse the issue. 

 Progress in the difficult field of biological re- 

 search seems to start from those points where 

 the situation is clear. The ever-present at- 

 tempts of the obscurantist to befog the issue 

 by over emphasizing what is not understood 

 is a procedure too familiar to call for more 

 than passing comment. Doncaster's book will 

 therefore serve to give balance to the situation 

 that is " developing normally." 



There are few minor points in the book that 

 call for comment. The author has, on the 

 whole, most judiciously assigned special dis- 

 coveries to their authors without overburden- 

 ing the text with names. The omission of 

 Stevens's name on page 63 in connection with 

 the discovery of the XY chromosomes in rela- 

 tion to sex determination is an oversight, 

 but some fuller mention might have been ex- 



pected in connection with the history of these 

 chromosomes when much less important mat- 

 ters receive their historical setting. 



T. H. Morgan 

 Columbia Universitt 



The Butterfly Guide: a Pocket Manual for 

 the Eeady Identification of the Commoner 

 Species found in the United States and 

 Canada. By W. J. Holland, LL.D. 3A X 

 5| inches; pp. 23Y; 295 figures in color. 

 Doubleday, Page & Co. Cloth. $1. 

 Any guide book to the identification of 255 

 species of butterflies, that contains 295 flnely 

 colored figures, that costs only a dollar and 

 actually does go into a vest pocket, may truth- 

 fully be called a great little book. This, in a 

 few words, is a fair description of Dr. W. J. 

 Holland's " Butterfly Guide." Apparently it 

 is the first of its kind, and also the last word 

 (and picture) in butterfly books for availabil- 

 ity in the fleld and home. 



The thirty-thousand-copy success of Dr. Hol- 

 land's original " Butterfly Book " may justly 

 be regarded as the inspiration for the present 

 elegant booklet; and the author's point is well 

 taken. This manual is built on the same gen- 

 eral lines as Chester A. Eeed's Pocket Bird 

 Guide Series, and the " Birds of New Jersey." 

 True enough, these volumes are none of them 

 "reading books," and in the business of fur- 

 nishing means to ends in identifying species 

 they stick closely to their trails. 



The purpose of this almost bewildering array 

 of colored butterfly pictures is to promote 

 identification of strange species, literally in a 

 moment; and right well do they serve their 

 purpose. Remembering as we do the breezy 

 and rare freshness of the author's literary 

 style, the only regret about this volume is that 

 it does not and can not furnish room for un- 

 limited HoUandesque gossip and disquisition 

 on the more interesting species. 



W. T. H. 



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