124 MENDELISM CHAP, xi 



the pollen grains eventually spring. Whether this may 

 turn out to be the true account or not, the possibility 

 must not be overlooked in future work. 



From all this it is clear enough that there is much to 

 be done before the problem of sex is solved even so far as 

 the biologist can ever expect to solve it. The possibilities 



Single 



Single Double 



Pollen of Y _ n-ii x. Ovule of 

 pure single 



Single Single Single 



I I , I- 



I 

 Single Single Double Single Double 



I I I I 



Single Single Double Single Double 



are many, and many a fresh set of facts is needed before 

 we can hope to decide among them. Yet the occasional 

 glimpses of clear-cut and orderly phenomena, which Men- 

 delian spectacles have already enabled us to catch, offer 

 a fair hope that some day they may all be brought into 

 focus, and assigned their proper places in a general 

 scheme which shall embrace them all. Then, though 

 not till then, will the problem of the nature" of sex pass 

 from the hands of the biologist into those of the physicist 

 and the chemist. 



