SCIENCE 



FRroAY, April 15, 1921 



CONTENTS 

 The Photochemistry of the Sensitivity of 

 Animals to Light : Dr. Selig Hecht 347 



The Mechanism of Injury and Becovery of 

 the Cell: Peofessoe W. J. V. Osterhout. 356 



Isao lijima: Propessor Bashpord Dean...,- 356 



Scientific Events: — 

 Ex-secretary Meredith on Research; Scien- 

 tific Legislation; Lectures iefore the Sioux 

 City Academy; Cooperation of National 

 Health Agencies; The American Meteorolog- 

 ical Society; The Edinburgh Meeting of the 

 British Association 357 



Soientifio Notes and News 360 



University and Educational News 363 



Discussion and Correspondence: — 

 Positive Bay Analysis of Lithium : Dr. A. J. 

 Dempster. A Remedy for Mange in White 

 Bats: Cornelia Kennedy. Impossible (?) 

 Stories: Professor Samuel G. Barton. . . 363 



International Scientific Orgamization 364 



He BooTcs: — 

 The Terrestrial Life associated with the 

 Coals of Northern France: Professor 

 Charles Schuchert 367 



Special Articles: — 



The Belativity Shift of Spectrum Lines: 

 Dr. Raymond T. Birge. A New High 

 Temperature Becord for Growth: Dr. D. T. 

 MacDougal 368 



The American Mathematical Society: Pro- 

 fessor R. G. D. Richardson 372 



MSS. intended for publication and books, etc., intended for 

 review should be sent to The Editor of Science, Garrison-on- 

 Hudson, N. Y. 



THE PHOTOCHEMISTRY OF THE 



SENSITIVITY OF ANIMALS 



TO LIGHTi 



I 



An analysis of sensory stimulation, in order 

 to be objective, must take its data from the 

 relations between the properties of the stimu- 

 lating agent and those of the responses of the 

 animal. If the analysis is to be quantitative 

 as well as objective, not only should the re- 

 sponse be a qualitatively invariable reflex but, 

 together with the source of stimulation, it 

 should be capable of precise and easy control. 



There are a number of animals which 

 possess such characteristic responses. Typical 

 of these are the ascidian, Ciona intestinalis 

 and the long-neck clam, Mya arenaria. Both 

 of these animals, when exposed to light, 

 respond by a vigorous retraction of the 

 siphons. It has therefore been possible to 

 investigate quantitatively the properties of 

 their photic sensitivity, and as a result to 

 propose an hypothesis which accounts for this 

 type of irritability in terms of an underlying 

 photochemical mechanism. 



I propose now to describe briefly the evi- 

 dence which has been accumulated in this 

 connection, and to present the outstanding 

 features of the proposed hypothetical mech- 

 anism. 



II 



The photosensory activities of these animals 

 possess four striking and important proper- 

 ties. (1) When exposed to light, the animal 



1 Delivered at th© Symposixim on General Physi- 

 ology held by the American Society of Naturalists 

 on Decemlber 30, 1920, at its Chicago meetings. 

 The paper was iUustraited with a number of charts 

 which are not reproduced here. They may be 

 found, together with the data on which this sum- 

 mary is based, in a series of articles in the Journal 

 of General Physiology from 1918 to the present 

 time. 



