802 



SCIENCE. 



[N. S. Vol. VII. No. 180. 



the markings of particular parts or areas. 

 Generally, it is not only this, but color diflfer- 

 ences combined with variations either in general 

 size or in the size of special parts or organs, in 

 which the variations of different parts are some- 

 times in opposite directions. If the author had 

 worked directly from large series of specimens, 

 instead of taking data tabulated by others rela- 

 ting to the single character of size, it is pretty 

 safe to say that the paper here under notice 

 would not have been written. 



In the case of Zapus there is no reason for 

 doubt in respect to the status of the two forms. 

 They present as clear and well jironouuced evi- 

 dence of specific distinctness as could well be 

 looked for between congeneric forms. In the 

 case of Scalops the curves of differentiation are 

 based on- the single character of general size, 

 the length of the skull being taken as the basis. 

 Other characters of perhaps equal or even 

 greater importance, as the increase in the size 

 of the teeth with decrease in skull length or in 

 general size, the relative length of the tail and 

 marked differences in color are ignored, per- 

 haps because the differences in these features 

 are not easily reducible to ' quantitative ex- 

 pressions.' But taking size alone, what kind 

 of a ' method' is it that attempts to determine 

 quantitative difference, say between Scalops 

 aquaticus from Massachusetts, Connecticut and 

 New York and Scalops machrinus from Minne- 

 sota, Illinois and Iowa by taking in the first 

 case a few specimens at irregular and infre- 

 quent intervals from Cape Cod to Charleston, 

 S. C, and in the other in a similar way from 

 Minnesota to Louisiana "? In either case the 

 difference in size is greater between specimens 

 from the northern and the southern points in 

 either series than between specimens from cor- 

 responding points in latitude between S. 

 aquaticus a,n6. S. machrinus! Mr. Davenport's 

 Fig. 8 thus shows nothing of any value what- 

 ever. The quantitative study of variation is a 

 problem of great interest and importance, but 

 this is not the way to go about it. The ideal 

 way, and one which would be profitable in 

 results, would be to take a sufficiently large 

 series of adult specimens, say in the case of 

 Scalops of not less than 20 to 50 from judiciously 

 selected localities not more than 100 miles 



apart, along at least two lines, the one merid- 

 ianal, the other on a parallel of latitude (due 

 regard in each case being had for differences of 

 elevation), and subject each available character 

 to quantitative analysis. Were this done 

 on a series of such intersecting lines extending 

 throughout the ranges of all the forms of a 

 genus the results might then be expressed in 

 curves that would reflect actual facts a,nd throw 

 important light on the status and real relation- 

 ships of all the forms involved. It might be 

 well worth doing, at least in the case of a few 

 groups, for the general bearing such results 

 would have on the problems of evolution ; but 

 the millenium of a precise knowledge of species 

 and subspecies for any class of animals — say of 

 North American mammals — will not arrive in 

 our day if we must wait for the production of 

 that delightful result by the process of quanti- 

 tative determination of character variation. 

 The work and expense involved is too great, 

 and long before final results would be available 

 the methods now in vogue of studying com- 

 paratively large series from as many localities 

 as possible will probably have already covered 

 and decided most of the points such an elabo- 

 rate system might be properly expected to 

 establish. 



J. A. Allen. 



A NECESSARY CORRECTION. 



To THE Editor op Science : In an article 

 claiming to be a review of ' The Living Sub- 

 stance' (Supplement to Journal of Morphology), 

 which appeared in Nature recently, the re- 

 viewer, F. A. D., says : " The authoress of this 

 wordy treatise informs us (p. 173) that she 

 started from a neutral position with regard to 

 Biitschli's vesicular theory, or even with a bias 

 against it. Now, however, having become the most 

 ardent of converts, she proceeds, with the proverbial 

 zeal of a proselyte, to carry the original doctrine 

 to extremes. Not content xvith proclaiming the 

 existence of foams undreamt of by BiUschli — 

 ' wheels ivithin wheels^ ad infinitum — she utters 

 ivhat amounts to a denunciation of all previous 

 statements of biological fact and theory as mislead- 

 ihg and inadequate, and urges in effect that the 

 whole science of life needs recasting from the new 

 point of view. ' ' 



