SCIENCE 



A Weekly Journal devoted to the Advancement 

 of Science, publishing the ofHcial notices and 

 proceedings of the American Association for the 

 Advancement of Science, edited by J. McKeen 

 Cattell and published every Friday by 



THE SCIENCE PRESS 



I 1 Liberty St., Utica, N. Y. Garrison, N. Y, 



Ne-w York City: Grand Central Terminal 



Single Copies, 15 Ct3. Annual Subscription, 86.00 



Entered as second-class matter January 21, 1922, at the Post 

 Office at Utica, N. Y., under the Act of March 3, 1879. 



VoL.LV February 3, 1922 No. 1414 



Species, Pure and Impure: Propessok Brad- 

 ley Moore Davis 107 



The Trend of Earth History: Propessor 

 Eliot Blackwelder 114 



The Agricultural Museum of the Argentine 

 Sural Society: Dr. F. Lamson-Scribner.... 119 



Scientific Events: 



The William Barton Rogers Science Sail 

 of the College of William and Mary; Me- 

 tirement of Professor Albert W. Smith; 

 The American School of Prehistoric Studies 

 in France; The History of Science at the 

 St. Louis Meeting of the American Histor- 

 ical Association ; Report on Membership of 

 the American Association for the Advance- 

 ment of Science 121 



Scientific Notes and News 124 



University and Educational Notes 127 



Discussion and Correspondence : 



Abraham Cowley and the Agricultural Col- 

 lege: Dr. E. J. H. DeLoach. The Lost 

 Foxhall Jaw: Dr. Henry Pairpield Os- 

 BORN. The Russian Bureau of Applied 

 Botany: D. N. Borodin. Memorial to 

 Wilhelm Wundt: Professor B. B. Titch- 



ENER , 127 



The Rhodesian STcull 129 



Special Articles: 



A Preliminary Attempt to Transmute 

 Lithium: Dr. Ealph W. G. Wyckopf. The 

 Effect of Sodium Hydrate on the Digesti- 

 bility of Grain Hulls: J. B. Lindsey 130 



The American Chemical Society: Dr. C. L. 

 Parsons 132 



SPECIES. PURE AND IMPURE^ 



There has come about in recent years a 

 profound modification of our conception of a 

 species in that tlie botanist, at any rate, is 

 compelled to recognize tlie fact that Nature 

 presents large numbers of successful kinds of 

 plants that reproduce their types either wholly 

 or in high percentages, but which clearly have 

 germinal constitutions of a hybrid character. 

 These forms may legitimately be described and 

 classified as species and they are frequently 

 virile lines of evolution making up groups of 

 individuals that readily maintain themselves in 

 suitable habitats. As assemblages of like 

 individuals, hybrid as to their germ plasm, they 

 present subjects of study that were not dif- 

 ferentiated by the earlier naturalists from the 

 populations of species as they viewed them. 



The test of a species, in addition to the 

 characters that distinguish it, has always been 

 the evidence that it breeds true to its peculiari- 

 ties or so nearly true that variations from the 

 type may be passed over in the descriptive 

 writings of the systematist as exceptions of 

 little importance to the mind seeking for order 

 and rebellious of mental disturbance in his 

 efforts to express this order in accounts of 

 faunas and floras over the earth. There are, 

 then, chiefly as the result of genetieal studies 

 of the near present, two conceptions of species. 



There is the pure species breeding true 

 because its germ-plasm in the diploid condi- 

 tion carries two similar sets of factors, each 

 set contributed by one of the parents and each 

 set having the same genetic make up except 

 for those factors responsible for sex and for 

 sex-linked characters. The pure species was 

 in the main the concept of Darwin and the 

 older naturalists, and it was assumed to be 

 representative of species. As viewed by the 

 eytologist, confident that chromosomes carry 



1 Address of the president of the American 

 Society of Naturalists, thirty-niuth annual meet- 

 ing, Toronto, December 29, 1921. 



