On the Teaching of Mathematics.

On the Teaching of Mathematics: DR. F. D. MuRRUDNEY. The Antibacterial Action of Penicillin NAGHAN . ...479 Algaoit Gram Negative Organmsms: DR. GLADYS L. Cultural Interchange Between the Soviet Union and HOBBY. Relation of Dosage to Survival Time of the United States: PROFESSOR STUART MUDD. 486 Arsenite-Injected Roaches: DR. J. FRANKLIN YEAObituary: GER and SAM C. MUNSON. The Motion of Small Frere Marke-Fetorin: PROFESSOR FRANCIS E. Particles in Magnetic Fields: BROTHER GABRIEL LLOYD and PROFESSOR JULES BRUNEL. Albert KANE and CHARLEs B. REYNOLDS ........................... 499 Kingsbury: PROFESSOR EDWIN B. DAVIS. Recent Scientific Apparatus and Laboratory Methods: Deaths .. . 487 The Blood-Saline Coagulation Time Test: D. ALScientific Events: FRE LEWIN COPLEY and DR. RALPH B. HOULIHAN. The American Academy of Tropical Medicine; A Constant Vacuum Apparatus: DR. JOHN W. The National Academy of Sciences; Medals CAMPBELL and DR. J. W. BEARD. ........................ 505 Awarded by the Royal Society; Award of the Science News ......... 10 Walter Reed Medal; Award of the Perkin Medal 489 Scientific Notes and News............................ 491 -Discussion: SCIENCE: A Weekly Journal devoted to the AdvanceUtilization of "Pore Spaces" of Semi-Permeable ment of Science. Editorial communications should be sent Membranes: WiLLIAM A. MOoL Improbability to the editors of SCIENCE, Lancaster, Pa. Published every and Impossibility: DR. H. M. DADOURIAN; ANATOL Friday by JAMES SHNEIDEROV ............. 494 Scientific Books: THE SCIENCE PRESS Mitosis: PROFESSOR C. W. METz .......... .............. 496 Lancaster, Pennsylvania Reports: Smith College Conference on Plant Embryo CulAnnual Subscription, $6.00 Single Copies, 15 Cts. ture: DrL ALBERT F. BLAKESLEE........................ 497 SCIENCE Is the official organ of the American AssociaSpecial Articles: tion for the Advancement of Science. Information regardThe Cholinesterases in the Light of Recent Finding membership in the Association may be secured from the office of the permanent secretary In the Smithsonian ings: PROFESSOR BRUNO MENDEL and HARRY Institution Building, Washington 25, D. C.