66 THE EVOLUTION OF LIVING BEINGS. 



easier seen in the case of the mossplant, the result of 

 a single gamete, than in the case of a diploid organism 

 because here the result is apt to be obscured by the 

 necessity of such a gamete to mate with another one, 

 of which we do not know whether it is changed in 

 the same sense, or not. 



The advantage of haploid organisms above diploid 

 ones is, in general, that we can choose directly the ga- 

 metes which we want to mate, by pairing morpho- 

 logically different haploid genwations, or better still 

 — as in the case of Spirogyra — by choosing and ma- 

 ting morphologically different gametes, while in the 

 case of diploid organisms we can only pair diploid indi- 

 viduals, and have no means to find out which of the 

 gametes produced by these, finally fuse, except by 

 judging after the result: the character of the diploid 

 organism, sprouting from the zygote thus obtained. 



So the study of haploid organisms may very well be 

 destined to give us the clue to the final causes of the 

 origin of species. 



For the present we know but very little about them; 

 of some known facts I wiU come to speak at the 

 end of this sketch. 



Experiments with mosses, seem to me, to be highly 

 recommendable. 



For the present we will have to stick to known facts, 

 and therefore will continue our discussion of the 

 origin of the differently constituted types of diploid 

 organisms which people the globe. 



