136 BREEDING 



that the result of a cross between a round and a 

 wrinkled is apparently a round identical with the 

 round parent, but is in reality a blend between the 

 round and wrinkled, is entirely missed. The vulgar 

 reluctance to be clear in the mind as to the things 

 which are represented by words used has not been 

 without its effect on the complexion of the Mendelian 

 doctrine as expounded by the less considerable of 

 its adherents. When a character has been found 

 to behave in Mendelian fashion in inheritance, it 

 is considered that the nature of the character and 

 its mode of inheritance have been determined ; and 

 that any further investigation of the matter is 

 superfluous. In this way a great many instances of 

 characters which apparently behave in a Mendelian 

 way in inheritance have been accumulated. But 

 as to the essential nature of the characters 

 themselves we are still ignorant. It is probable 

 that, when the seven pairs of characters investigated 

 by Mendel have been thoroughly worked out, the 

 terms now used to designate these characters will 

 have no more than the most remote application to 

 them, and that, for the purpose of accurately repre- 

 senting the essential nature of these characters, 

 they will be wholly valueless. 



It is here that the value of a theory like the 

 presence and absence hypothesis comes in. This 

 hypothesis leads to the investigation of the nature 

 of the characters themselves. This is its chief 

 value. If it does not do this, if it is used merely 

 to restate already known facts in new terms, it is 



