October 6, 1905.] 



SCIENCE. 



431 



L. E. Dickson : ' On the quaternary linear 

 homogeneous groups modulo p of order a multiple 

 of p.' 



L. E. Dickson : 'On finite algebras.' 

 Virgil Snydkr : ' On a type of rational twisted 

 curves.' 



E. J. TowNSEND : ' Arzela's condition for the 

 continuity of a function defined by a series of 

 continuous functions.' 



H. S. White : ' Rational plane curves as related 

 to Riemann transformations.' 



F. R. MouLTON : ' A class of periodic solutions 

 of the problem of three bodies.' 



C. IST. Haskins : ' Note on the differential in- 

 variants of a surface and of space.' 



E. V. Huntington: 'The continuum as a type 

 or order: an exposition of the modern theory.' 



The next meeting of the society will be held 

 at Columbia University, on Saturday, October 

 29. The San Francisco section meets at the 

 University of California, on September 30. 

 The annual meeting of the society for the 

 election of officers will be held on Thursday 

 and Friday, December 28-29. 



F. ]Sr. Cole, 

 Secretary. 



DISCUSSION AND CORRESPONDENCE. 

 THE PROBABLE ORIGIN OF CERTAIN BIRDS. 



In a recent article in Science,^ Mr. W. E. 

 D. Scott attempts to apply the ' mutation ' 

 theory of de Vries to the origin of certain 

 puzzling forms of North ^American birds, his 

 conclusion being: 



In the light of the evidence set forth [in the 

 preceding pages of his article] only one answer 

 can be made to the question as to the part the 

 process defined by de Vries as ' mutation ' is play- 

 ing among higher animals to-day. Beyond doubt 

 we have witnessed the birth of new species of 

 birds during the past seventy years. Moreover, 

 some of these new species have flourished so as to 

 have become a salient part of the bird fauna in 

 the region where they occur and where they were 

 unknown to skilled ornithologists, who carefully 

 studied these regions in the early part of the 

 last century. 



The birds here considered by Mr. Scott are 

 nine in number, all from the ' Hypothetical 



^ ' On the Probable Origin of Certain Birds,' by 

 William E. D. Scott, Science, N. S., Vol. XXII., 

 No. 557, Sept. 1, 1905, pp. 271-282. 



List ' of the American Ornithologists' Union 

 Check-List of North American Birds, and, in 

 the order of discovery, are as follows: Small- 

 headed warbler (Muscicapa minuta Wilson,. 

 1812), Blue Mountain warbler (Sylvia mon- 

 tana Wilson, 1812), carbonated warbler {Sylvia 

 carhonata Audubon, 1831), Cuvier's kinglet 

 (Begulus cavierii Audubon, 1832), Townsend's- 

 bunting (Emheriza townsendii Audubon,. 

 1834), Cooper's sandpiper (Tringa cooperi 

 Baird, 1858), Brewster's linnet (Acanihis- 

 hrewsterii Kidgway, 1872), Lawrence's warbler 

 (Helminthophaga lawrencei Herrick, 18Y4),, 

 Brewster's warbler {Helminthophaga leuco- 

 hronchialis Brewster, 1876). The first four 

 of these birds are known only from the de- 

 scriptions and figures given of them by Wilson 

 and Audubon; of each of the next three, the 

 original and ' still unique type specimen is 

 preserved. The remaining two, both forms of 

 Helminth ophila, are known from numerous 

 examples, they being of more or less frequent 

 occurrence (if we reckon the variants of each) 

 over a limited area in southern 'New England 

 (mainly the lower Connecticut Valley), the 

 lower LIudson Valley and northern ISTew 

 Jersey. 



Mr. Scott comments on the first seven very 

 briefly, but states, in concluding the enumera- 

 tion, that he is compelled ' to consider these 

 forms as mutations (which were not perpetu- 

 ated) from species still existing.' About 

 seven pages are then devoted to the remain- 

 ing two forms, Helminthophila leuco-' 

 hronchialis and H. lawrencei, in which he 

 gives a partial list of the known captures of 

 each, mostly in footnotes in small type, with 

 more or less extended extracts from the records 

 relating to them, and often a summary of the 

 opinions that have been expressed regarding 

 the status and relationships of the two forms. 

 The number of specimens of H. leuco- 

 tronchialis at present extant is estimated to- 

 be ' at least 150,' and of H. lawrencei ' between 

 20 and 25.' 



These two forms are discussed separately, 

 at some length. Under H. leucohronchialis 

 {I. c, p. 278), he expresses ' his conclusions re- 

 specting them as follows : 



