Latent Characters 225 



not by physiological, but only by morphological 

 research. And the claims of these two great 

 lines of inquiry are obviously very diverging. 

 Morphological or comparative studies need 

 a material standard, by which it may be readily 

 decided whether certain groups of ani- 

 mals and plants are to be described or de- 

 nominated as species, as subspecies or as varie- 

 ties. To get at the inner nature of the dif- 

 ferences is in most cases impossible, but a de- 

 cision must be made. The physiological line 

 of inquiry has more time at its disposal ; it calls 

 for no haste. Its experiments ordinarily cover 

 years, and a conclusion is only to be reached 

 after long and often weary trials. There is no 

 making a decision on any matter until all 

 doubtful points have been cleared up. Of 

 course, large groups of facts remain uncertain, 

 awaiting a closer inquiry, and the teacher is 

 constrained to rely on the few known instances 

 of thoroughly investigated cases. These alone 

 are safe guides, and it seems far better to trust 

 to them and to make use of them for the con- 

 struction of sharp conceptions, which may help 

 us to point out the lines of inquiry which are 

 still open. 



Leaving aside all such divisions and defini- 

 tions, as were stamped with the name of pro- 

 visional species and varieties by the great sys- 



