August 22, 1919] 



SCIENCE 



177 



Returning to the example under considera- 

 tion we find that the great spurts in the ad- 

 vance are due to the stimulation of the scien- 

 tific imagination by hypotheses which aim to 

 bridge the gulf between the two lines of re- 

 search. The idea of a connection between the 

 fact of the general equality of male and fe- 

 male parents in heredity, and the fact of 

 equality in the nuclei of the male and female 

 sex-cells was of epoch-making importance. 

 Later the association of the precise though 

 complicated behavior of the nuclear bodies 

 called chromosomes with the possibility that 

 these bodies are the bearers of the hereditary 

 factors again caused a tremendous advance 

 along both of the lines we have mentioned. 

 More recently still, the hypothesis has been 

 made that certain jieculiarities in linkage of 

 characters may be associated with peculiarities 

 in the behavior of the parts within single chro- 

 mosomes. If you will pardon my digression 

 into this field I will elaborate the last step. 

 According to the view that the chromosomes 

 are the bearers of the hereditary factors it 

 seemed clear that the factors located in a 

 single chromosome must always go together 

 and a corresponding linkage of adult char- 

 acters in four groups corresponding to the 

 number of chromosomes was made out for the 

 fruit fly, Drosophila. But it was then dis- 

 covered that the linkage was not complete. 

 Occasional separation took place and the per- 

 centage of such separations was found to be 

 definite for any two characters of such a 

 linked group. Still further it was shown that 

 knowing the percentage of such breakings of 

 the linkage between characters A and B and 

 between B and C the percentage of breaking of 

 linkage between A and C could be calculated. 

 It was either the sum or the difference be- 

 tween the first two cases. On this basis the 

 factors in a linked group were arrayed in a 

 linear series in which the actual breaking of 

 linkage between any two points closely followed 

 the expectation. Such a series was extremely 

 interesting and the elaboration and perfection 

 of the series in the various groups of plants 

 and animals in itself would have furnished 

 endless opportunity for research. But the in- 



terest in the series was immediately greatly 

 stimulated by the suggestion that these phe- 

 nomena of inheritance of adult characters 

 could be explained by certain peculiarities in 

 the behavior of the chromosomes. By this 

 suggestion the fields of experimental breeding 

 and of cytology were again brought into con- 

 nection and there is gradually developing a 

 fruitful hypothesis which in some respects 

 bears the same relation to heredity that the 

 atomic theory does to chemistry. Even if the 

 direct hypothesis proves to be premature it 

 will have been the means of opening up lines 

 of research which otherwise would have re- 

 mained untouched. 



I have taken the time to give this example 

 from the field of biology in order to emphasize 

 my point in urging you to encourage any 

 tendency you may have toward visions of re- 

 lationship between things that at first seem to 

 be wholly different. Young investigators are 

 often inclined to think when an idea comes to 

 them that it can not be of value because no 

 one else has ever followed it up. Besides I 

 have heard it said that it is one of the fimc- 

 tions of a teacher of graduate students to see 

 that they do not waste their time following up 

 unprofitable ideas of their own. This would 

 be very well but for the unfortunate consider- 

 ation that to many, only well-established ideas 

 are profitable, and therefore new ideas are 

 always considered as unprofitable. This is 

 stand-patism in science and the stand-patter 

 in this field should have even less sympathy 

 than the stand-patter in politics. Our salva- 

 tion as original investigators depends upon 

 the development of our own ideas. The ques- 

 tion may be raised whether it is ever un- 

 profitable for a person to follow out his own 

 ideas. Is it not of more value to us personally 

 to follow up an idea of our own even if it be 

 wrong than it is to prove the truth of a dozen 

 ideas suggested to us by others? But, your 

 idea is not necessarily wrong and the fact that 

 it is your own makes it extremely valuable. 

 As your own it enables you to draw on the 

 fund of extra energy which we all possess but 

 which only a personal, living interest can draw 

 out. Only such ideas, to use the words of our 



