44 NATIONAL TRENDS IN BIOLOGY 



get further until they are pulled out by some other partial 

 discipline. The side path was passed by unheeded, be- 

 cause they could not and cannot look in more than a 

 single direction — most biologists have only small hori- 

 zons. To every age, the problem or problems will seem to 

 be of greatest importance where some of the great per- 

 sonalities of that special epoch casually are leading 

 others." 



More than one writer speaks of the "fads and fancies" 

 which have taken hold in biology at various times, and 

 these men call attention to the fact that we have but to 

 examine the scientific journals to see the successive waves 

 of contributions on tropisms, artificial parthenogenesis, 

 cytology, spermatogenesis, regeneration, genetics, tissue 

 culture, endocrines, etc., which have come and gone. There 

 seems to be some one stimulus for such work, which springs 

 from some particular discovery that promises a way out 

 of the mechanistic dilemma, that is, which promises some 

 light on a mechanistic explanation of living phenomena. 

 INIany then start work on a problem and pile up appar- 

 ently stronger evidence, only to find themselves at sea 

 more than they were before. That particular problem is 

 then dropped, and work is begun on another, followed by 

 the same result. This procedure necessitates intensive 

 work which leads to quick results, and has its advantages, 

 of course, but instead of following the problems out with 

 some degree of finality, it gives up and another fad is 

 followed. 



Back of all experimentation, the impetus seems to come 



