Origin of Peloric Toadflax 463 



are valuable for the elucidation of general prob- 

 lems and broad features of the whole pedigree, 

 but the narrower and more practical question as 

 to the genetic relation of the single forms to one 

 another must be studied in another way, by 

 direct experiment. The exact methods of the 

 laboratory must be used, and in this case the 

 garden is the laboratory. The cultures must 

 be guarded with the strictest care and every 

 precaution taken to exclude opportunities for 

 error. The parents and grandparents and their 

 offspring must be kept pure and under control, 

 and all facts bearing upon the birth or origin of 

 the new types should be carefully recorded. 



Two great difficulties have of late stood in 

 the way of such experimental investigation. 

 One of them is of a theoretical, the other of a 

 practical nature. One is the general belief in 

 the supposed slowness of the process, the other 

 is the choice of adequate material for experi- 

 mental purposes. Darwin's hypothesis of nat- 

 ural selection as the means by which new types 

 arise, is now being generally interpreted as 

 stating the slow transformation of ordinary 

 fluctuating divergencies from the average type 

 into specific differences. But in doing so it is 

 overlooked that Quetelet's law of fluctuating 

 variability was not yet discovered at the time, 

 when Darwin propounded his theory. So there 



