September 22, 1922] 



SCIENCE 



323 



chemistry texts for them and for the vast 

 amount of time and thought they have spent 

 in the preparation thereof. I often wonder, 

 however, if the college teacher who lives and 

 works among college students and does some 

 research on the side can be expected to guage 

 the needs of the secondary student and to put 

 himself in the place of the secondary school 

 teacher. If such a college man could have an 

 opportunity to fill the position of a secondary 

 school teacher of chemistry for a period of say 

 five years, and have to make his living thereby, 

 I'd welcome a text he might produce. Or 

 must we wait till the profession of chemistry 

 teaching in secondary schools has become suffi- 

 ciently established, to attract men of the requi- 

 site scholarship, knowledge of chemistry, 

 acquaintance with what the colleges should re- 

 quire for entrance, and above all a close knowl- 

 edge of the mental equipment of students of 

 secondary school age before we can expect a 

 solution of the problem : ''What should be 

 taught in first year chemistry and how should 

 it be presented?" 



WlLHELM SeGBRBLOM 



Phillips Exetee Academy 



THE PHYSICO-CHEMICAL MECHAN- 

 ISM OF MUTATION AND 

 EVOLUTION 



It is the general rule in biology that 

 descendants resemlble parents, and that a 

 parent organism can not pass on to offspring 

 a factor which the parent did not receive from 

 the germ-plasm of its immediate progenitors. 

 Many apparent exceptions to this general rule 

 have been traced to the existence in the parent 

 gametes of recessive factors, which, while sup- 

 pressed in the parent, may be liberated again 

 in the offspring. Whether we accept the view 

 of Darwin that large differences can represent 

 the summation of small differences, or the more 

 probable view of Bateson and others, that mu- 

 tation or variation is a definite physiological 

 event, no satisfactory explanation has been 

 given as to the origin or source of these excep- 

 tions to the general rule of resemblance, 

 although they constitute the steps by which 

 evolution haltingly proceeds. 



The crying need that we must find a chem- 



ical, physical or physico-chemical basis for 

 mutation or variation has been voiced by many. 

 Thus in his address before the British Asso- 

 ciation for the Advancement of Science (Aus- 

 tralia, 1914, reprinted in Smithsonian Report, 

 1915, pp. 359-394), Sir William Bateson says: 

 "Every theory of evolution must be such as 

 to accord with the facts of physics and chem- 

 istry, a primary necessity to which our prede- 

 cessors paid small heed. ... Of the physics 

 and chemistry of life we know next to nothing. 

 Somehow the characters of living things are 

 bound up in properties of colloids, and are 

 largely determined by the chemical powers of 

 enzymes, but the study of these classes of 

 matter has only just begun. Living things are 

 found by simple experiment to have powers 

 undreamt of, and who knows what may be 

 behind?" 



Keeently R. S. Lillie'- (Science, 51, 525, 

 1920) has stressed the importance of physico- 

 chemical investigation of protoplasm, and 

 Alexander Forbes (Science, 52, 331, 1920) has 

 called for closer cooperation between physicists 

 and biologists in attacking biological problems. 

 An attempt will be made here to outline cer- 

 tain basic physico-chemical principles which 

 affect the formation, development, growth and 

 reproduction of living things, and to point out 

 how it is possible for variation in some of the 

 factors therein involved to account for im- 

 portant and transmissible variations or muta- 

 tions in individual organisms. 



At the outset let it be stated that no mys- 

 terious or special "vital force" will be evoked, 

 but that the well-known forces that control 

 inanimate matter seem quite sufficient for the 

 purpose. 



In nature, both animate and inanimate, the 

 following basic factors tend to produce sym- 

 metrical orientation or aggregation: (1) 

 Crystallization; (2) Diffusion, as in the forma- 

 tion of Liesegang's rings, agate, etc.; (3) Elec- 

 tric or magnetic fields of force; (4) Harmoni- 

 ous vibration as of air, water, etc. We here 

 disregard mere chance and the conscious ar- 

 rangement by man. 



1 See also Lillie 's interesting papers in Biolog- 

 ical Bulletin, 1917-1919, and Scientific Monthly, 

 February, 1922. 



