466 



SCIENCE. 



[N. S. Vol. XXIII. No. 586. 



doah at Harpers Ferry are to be held, in a 

 series of screened troughs, a few thousand 

 specimens of the Mount Vernon form, in an- 

 other series a mixture of equal numbers of 

 Mount Vernon and Harpers Ferry specimens, 

 a third series to be empty as a cheek upon the 

 results. At Mount Vernon or at the southern 

 limit of the range of the species, and at Wash- 

 ington, these series are to be repeated. Such 

 trials would be expected to yield interesting 

 and valuable, even if negative, results. 



Under the title ' The Nature of Evolution- 

 ary Motion ' Mr. O. F. Cook gave an exposi- 

 tion of his kinetic theory, and showed how the 

 interpretation of evolutionary factors differs 

 from that of other doctrines. It was held, in 

 particular, that isolation and natural selec- 

 tion are not at all factors of evolution in any 

 strict and scientific sense; they conduce to 

 the differentiation of new species (speciation), 

 and to increased fitness (adaptation), but have 

 no power to actuate the process of organic 

 change in species (evolution). The principal 

 agent of evolutionary progress is the normal 

 interbreeding of the normally diverse indi- 

 viduals of which species are composed. Evolu- 

 tion is thus an intraspecific phenomenon, in- 

 stead of being interspecific. The intraspecific 

 differences which contribute most to evolu- 

 tionary motion are not those which arise as 

 adjustments to different conditions of the en- 

 vironment (artism), but those which are inde- 

 pendent of environmental adjustments (heter- 

 ism). 



Outlines and diagrams were shown in ex- 

 plaining the bearing of these distinctions upon 

 the four principal types of evolutionary the- 

 ories, static, saltatory, determinant and kin- 

 etic. Static theories were defined as those 

 which view the species as normally stationary, 

 though moved occasionally by environmental 

 causes. Saltatory theories prescribe motion 

 of an intermittent character and at remote 

 intervals. Naegeli's determinant theory held 

 that species move in a single definite direction 

 as a result of causes inherent in the organisms. 

 The kinetic theory provides for an indeter- 

 minate, composite motion resulting from the 

 continuous interbreeding of the diverse indi- 

 viduals of the species. Selection does not 



cause this motion, but can restrict and deflect 

 it, and can thus lead evolution in adaptive 

 directions. Saltatory and determinant the- 

 ories do not provide for any practical adaptive 

 influence on evolution. Although completely 

 denying the current assumption that selection 

 is the cause or active principle of evolution, 

 the kinetic theory provides better than any 

 other for a practical explanation of the man- 

 ner in which selection induces adaptation. 



The 413th meeting was held March 3, 1906, 

 President Knowlton in the chair and thirty- 

 two persons present. Dr. L. 0. Howard pre- 

 sented the first paper on ' The Gypsy Moth and 

 the Brown-tailed Moth and the Introduction 

 of their European Parasites,' illustrated with 

 lantern slides. He described the accidental 

 introduction of the gypsy moth into Massa- 

 chusetts by the escape of an egg mass from 

 some breeding experiments in 1868. In 1900 

 after spending a million dollars in fighting 

 the insect the state stopped the work and the 

 moth gained ground until last year when the 

 state appropriated $300,000 to be spent during 

 three years. $10,000 was also appropriated 

 for the introduction of its parasites and one 

 half this sum was turned over to Dr. Howard 

 for the furtherance of this object. He has 

 imported from Sardinia 2,500 of the parasite- 

 infested larvse. The moth has American 

 parasites, but the percentage of infected larvae 

 is lower, and the tree infection much greater 

 in America than in Europe. The illustra- 

 tions showed graphically the entire defoliation 

 of trees caused by the caterpillars and the large 

 scale in which the campaign against them is 

 conducted,^by banding trees, creosoting the 

 egg masses and burning over underbrush with 

 the blast torch. 



The brown-tailed moth was brought over in 

 the winter cocoon stage, a nest of leaves bound 

 together and containing larvas. Unlike the 

 gypsy moth the adult is a good flier and, there- 

 fore, disseminates more directly and rapidly 

 and its spread is a foregone conclusion. 



Professor A. S. Hitchcock read a paper en- 

 titled ' A Synopsis of the Genus Tripsacum.' 



Tripsacum is a genus of grasses extending 

 from the southern United States to South 



