INBREEDING, PARTHENOGENESIS, ASEXUAL REPRODUCTION 257 



of the kind can so rarely be clearly demonstrated that I cannot lose 

 the opportunity of calling attention to it. The germ-plasm of this 

 OpJirys must have varied at an earlier stage, for otherwise the detach- 

 ment of the pollinia would not have become normal and hereditary, 

 but it can only have varied to the extent that the structure of this 

 one small part of the flower was affected by the variation : something- 

 must have varied in the germ-plasm that had no influence upon the 

 other parts of the flower, that is, solely the deterininants of the pollinia. 



Let us return after this digression to our previous train of 

 thought ; we have to inquire how we can interpret the fact of con- 

 tinued self-fertilization without any visible injurious results to the 

 species. If cross-fertilization be a material advantage as regards the 

 continuance of the species, how can it be transformed into its opposite 

 without evil effects '? And there are no visible evil effects in Ophrijs 

 apifera. It is indeed not so abundant as Opkrys inuscifei'a, or other 

 allied species, but it certainly does not follow from that that it is on 

 the way to extinction ; certainly no decrease either of vigour of growth 

 or of fertility can be observed. 



If we inquire from the standpoint of our theory, how the com- 

 position of the germ-plasm must have altered through continual 

 inbreeding, we have already found the answer — that through the 

 reduction of the number of ids at the maturation of every germ-cell 

 the diversity of the germ-plasm would gradually be lessened, that the 

 number of diflerent ids would thereby be lessened possibly even to the 

 identity of the whole of the ids. 



The consequences of such extreme uniformity of the germ-plasm 

 would not, according to our theory, necessarily be that the species 

 would be incapable of continued existence, but it would be that the 

 species would become incapable of adaptations in many directions. 

 Adaptations in one direction, such, for instance, as the variation in the 

 mode of attachment and detachinent of the pollinia of an Orchid, 

 would still be possible. Thus a species which has long been perfectly 

 adapted will be able to make the transition to inbreeding without 

 injury to its chances of continued existence, if it be compelled by 

 circumstances to do so. Species, on the other hand, which are still 

 undergoing considerable transformations in many directions must be 

 exposed by these to the danger of degeneration, just as happens in 

 the artificial experiments with domesticated animals, whose secret 

 weaknesses are greatly exaggerated by inbreeding. 



We might be inclined to regard the effects of inbreeding as 

 similar to those of parthenogenesis ; they are certainly analogous, for 

 both modes of reproduction must lead to a certain degree of uniformity 

 II. S 



