536 



SCIENCE. 



[N.S. Vol. XXI. No. 536. 



from the opening sentences of de Vries's 

 celebi'ated work, "asserts that the charac- 

 ters of organisms are built up out of units 

 distinctly different from one another. 

 These units may be combined to form 

 groups, and in allied species the same units 

 and groups keep recurring. Transitions, 

 however, such as are so abundantly repre- 

 sented in the outer forms of plants and 

 animals no more occur between these units 

 than between the molecules of chemistry." 

 It follows as a corollary from this state- 

 ment that species gnust be conceived to arise 

 from preexisting species by discontinuous 

 variations, or mutations, and not by fluc- 

 tuating variations, or variations proper. 

 The theory is built on a number of remark- 

 able facts derived from breeding organisms, 

 with special attention to their morpholog- 

 ical characters or attributes. I have been 

 asked to consider the question as to whether 

 the theory will apply also to the behavior 

 or ethological, as well as to the morpholog- 

 ical, aspect of organisms. 



The biologist finds it well to distinguish 

 carefully between structure and function, 

 just as the psychologist finds it greatly to 

 his advantage to distinguish sharply be- 

 tween the psychic, on the one hand, and the 

 physiological and morphological, on the 

 other. For the purposes of discussion I 

 will take the standpoint of the biologist in 

 so far as it relates to the distinction be- 

 tween structure and function, but I will 

 combine under function both the physiolog- 

 ical and psychological aspects cis together 

 constituting ethology, at any rate to the 

 extent that they are involved in the be- 

 havior of organisms. 



Now, inasmuch as ethology deals with 

 processes, or phenomenal diversity in time, 

 whereas morphology deals with the spatial 

 diversity of phenomena, it is evident that 

 ethological must be very different from 

 morphological characters. It might even 

 be said that the ethologist has no right to 



speak of a process as a character or char- 

 acteristic, and the original Greek meaning 

 of these words would seem to limit their 

 use to the structural configurations result- 

 ing from specific acts or processes. This 

 need not prevent us, however, from extend- 

 ing the meaning of the terms to include 

 also the typical and specific reactions of 

 the organisms to their environment. Cer- 

 tainly in the case of the human species, 

 which is best known ethologically, the terms 

 character and characteristic are hardly 

 used of physical structures, but almost ex- 

 clusively of typical modes of activity. 



In its application to ethology the muta- 

 tion theory can only mean that organic 

 species must differ from one another by 

 discrete idiosyncrasies of behavior. ]\Iost 

 biologists would probably regard any dis- 

 cussion of mutation from the ethological 

 standpoint either a.s superfluous or as 

 necessarily and merely confirmatory of 

 the results of morphological study. In 

 their opinion it would follow as a matter 

 of course that the functional and etholog- 

 ical characters of organisms must fluctuate 

 or mutate according as the structural char- 

 acters vary continuously or diseontinuous- 

 ly. In my opinion this is not so self- 

 evident as it would appear to be at first 

 sight. 



It is true, of course, that the various 

 structural categories from the phylum 

 down to the species, subspecies, variety, 

 sex and individual— all show what may be 

 regarded as correlated or corresponding 

 ethological characters, although this corre- 

 spondence is often very loose, vague and 

 irregular, for it is evident that slight 

 morphological may be correlated with com- 

 plex ethological characters, and conversely. 

 Some such correspondence may also be ob- 

 served in hybrid forms. All this is usually 

 taken for granted, and as a consequence 

 the theory of an ethophysical parallelism, 

 on the model of the famous psychophysical 



