416 



SCIENCE. 



[N. S. Vol. IX. No. 220. 



changes in the physiography of the region 

 (Weldon). Such facts indicate that species 

 are changing in essential specific characters 

 and sometimes rather rapidly changing. The 

 changes are notsuflBcient to be detected in cases 

 where the descriptions are wholly qualitative 

 or based upon the observation of a few indi- 

 viduals. But where a large number of in- 

 dividuals, taken at random, are measured the 

 modes may be used as standards for reference. 

 With the aid of such standards we can observe 

 not only the fact of change, but the rate and the 

 direction, and draw conclusions concerning the 

 causes of specific change. If two modes occur 

 in a species in one locality we can determine 

 whether they separate farther and farther from 

 each other, and the rate of such separation. A 

 careful correlation of the facts of separation of 

 modes with changes in environment will give 

 us an insight into the causes of specific differ- 

 entiation. In a word, the establishment of 

 these place-modes for various species in various 

 localities is the first sure step toward the solu- 

 tion of the problem of the Origin of Species. 



The methods of this work are very simple. 

 They involve the measurement of size, of pro- 

 portions and other elements of form, and of 

 color, by the color wheel ;* they involve also 

 counting repeated organs. The measurements, 

 or counts, are to be grouped into classes on the 

 basis of size. The means of measurement will 

 naturally be found ; but, most important of all, 

 far more significant than the mean, is the mode 

 or the most frequented class. The mode gives 

 the typical condition of the lot of individuals 

 measured. 



The end of the old century or the beginning 

 of the new one is a convenient time for making 

 a number of these determinations, and it is on 

 this account that I write to suggest to field 

 naturalists that for a year or two they bend 

 their efforts to the determination of place-modes. 

 I am so convinced of the importance of this 

 work that I am planning, with the cooperation 



*The color wheel is an instrument for determining 

 the percentage of constituent elementary colors in any 

 compound color. A small, cheap and convenient 

 form o£ this instrument^called the color top — with 

 standard colors may be bought for six cents of The 

 Milton Bradley Company, Springfield, Mass. 



of students, to work on this subject at the labo- 

 ratory at Cold Spring Harbor during the com- 

 ing summer, and I hope that simultaneous co- 

 operative observations may be made at Woods 

 Holl and other marine laboratories as well as at 

 the various inland stations and by private col- 

 lectors elsewhere. There is no fear of duplica- 

 tion of work, for two persons will hardly study 

 the same species in one and the same locality. 

 Chas. B. Davenport. 

 Haevakd Univeebity, March 2, 1899. 



IDENTITY OF COMMON AND LABRADOR WHITE- 

 FISH. 



The Common Whitefish of the Great Lakes 

 was first very imperfectly described by Dr. 

 Samuel L. Mitohill, in The American Monthly 

 Magazine and Critical Review for March, 1818. 

 The description, in fact, is so unsatisfactory that 

 his contemporaries and later ichthyologists for 

 more than fifty years supposed it to refer to the 

 Cisco, or Lake Herring, Argyrosomus artedi. A 

 good account of the Whitefish was published 

 by Richardson in 1836, under LeSueur's name 

 of Coregonus alhus, a name published only a few 

 weeks later than that of Mitchill ; but, like 

 Mitchill's, unaccompanied by a sufficient de- 

 scription. 



In 1836 Richardson established a new species 

 of Coregonus upon a dried specimen which he 

 received from Musquaw River, that falls into 

 the Gulf of St. Lawrence, near the Mingan 

 Islands, giving it the name Salmo (Coregonus) 

 labradoricus. This has been retained in the 

 literature as a distinct species up to the present 

 time, although its close relationship to the 

 Common Whitefish has sometimes been ob- 

 served without recorded comment. 



Systematic ichthyologists have found it diffi- 

 cult to show clearly the differences between. the 

 Common Whitefish and the Labrador Whitefish, 

 as may be seen by referring to the monographs 

 upon the Whiteflshes by Jordan and Gilbert, 

 Bean, and Evermann and Smith. They have 

 been forced to rely, finally, upon a single char- 

 acter, the presence of several rows of teeth on 

 the tongue to distinguish the two forms, and 

 this was supposed to be constant and in- 

 fallible. 



The writer has recently had occasion, while 



