No. 548] SHORTER ARTICLES AND DISCUSSION 493 



mated with brown animals which invariably lack agouti. 

 There were produced 15 young, of which 7 were yellow, 5 agouti 

 and 3 black or brown. Evidently the yellow parent transmitted 

 non-yellow (black or brown) in 5 cases associated with agouti, 

 and in 3 cases not so associated. On Sturtevant's hypothesis all 

 non-yellow young should have been agouti. 



C. C. Little 



Laboratory of Genetics, 



Bussey Institution, Harvard University, 

 June 17, 1912 



PHYSICAL ANALOGIES OF BIOLOGICAL 



Two schools or methods of thinking of heredity and other 

 general problems are recognized among biologists. Some hold 

 that all biological phenomena are to be explained in terms of 

 physical and chemical properties of unorganized matter. Others 

 are inclined to believe that the activities of living matter repre- 

 sent agencies or relations not shown in the inorganic world. The 

 first view has been called materialism, the second vitalism. 



These distinctions are not as important as sometimes supposed, 

 because of our inadequate knowledge of the properties of matter, 

 whether organic or inorganic. The materialistic view may be 

 said to have a practical advantage in encouraging the investiga- 

 tion of the physical and chemical phenomena of the organic 

 world, but vitalism may claim at least an equal advantage in 

 permitting the recognition of facts that lie on the other side of 

 the biological field, where the analogies of physics and chemistry 

 find little or no application. Thus the specific constitut.un or 

 speciety of living matter, the fact that organisms maintain their 

 existence and make evolutionary progress only in groups o 

 individuals united into specific networks of descent, mvohvs tin- 

 recognition of a condition or property quite foreign to the usua 

 conceptions of the physicist or the chemist. Yet this i.n.v.-rsal 

 condition of speciety must be considered as a general basis oi 

 background for any strictly biological study of the u^.ii..- 

 world. We may count, weigh, measure or analyze the bodies 

 and activities of organisms from as many other standpoints as 

 we please, but it is idle to draw general biological conclusions 

 from any merely mathematical or physical data. The true 

 biological significance of statistical and physical facts has to oe 

 determined by biological analysis. g 



As long as physical and mathematical analogue act some- 

 thing to our comprehension of biological tacts they are en 



