No. 534] THE PURE LINE THEORY 



363 



no critical bearing on the pure line problem. 34 This is 

 also true of numbers of other smaller experiments which 

 can not be cited. 



If one turns from the strictly pure line side of the 

 problem to the more general questions of the "some- 

 thing" or "Etwas" in the germ plasm which determines 

 in large degree the somatic characters of the individual 

 which develops from it, one can only suggest that nothing 

 whatever is explained by giving another name to a well- 

 known fact. Kvor since the time of Darwin, and before, 

 we have known that there was ''something" in the germ 

 cells which determined the character of the offspring. 

 We have had a dozen different names for this something, 

 and by adding a thirteenth, "Gene," Johannsen has 

 merely burdened us with another cloak for our igno- 

 rance. Unfortunately biological closets are full of such 

 cloaks, once in fashion— now out. 



Finally, I must make my own position quite clear. 

 With Professor Jennings's contention that pure line cul- 

 tures are of fundamental importance in many fields of 

 physiology and genetics, I am in hearty agreement. 

 Like other breeds of facts, "pure line facts" can not be- 

 come too abundant. Indeed, a priori, I am not opposed 

 to the genotype theory. As a theory it is most attract- 

 ive, hut one can not accept it without proof on that ac- 

 count. Personally, I am one of "that last small rem- 

 nant" who believe that in a problem of this kind the 

 proof must be biometric. This means merely three 

 things. In so far as the nature of the material permits, 

 all the data considered must be quantitative. The data 

 must be numerous enough that biological relationships 

 will not be obscured bv the errors of random sampling. 

 The data must be analyzed by logically sound methods. 



genotype or pure line theory. 



34 Naturally, this is purely a matter of interpretation, and does not 

 diminish in the slightest degree the value of the work. 



