170 On the Reproductive Functional [No. &, 



but we here see that it is more particularly, if not altogether 

 confined to the male element. Now, as the results of hybridisation 

 show that the pollen is more susceptible to the concomitant sterilising 

 action of hybridism than the female element, may we not suppose 

 that the debilitating effect of continued self-impregnation will also 

 manifest itself more quickly in the male than in the female element, 

 and thus afford an explanation of the decreased sexual powers of the 

 male, as compared with the female element, in the yellow varieties of 

 the above species of Verbasca furthermore, showing us that as it 

 has been a slowly acquired quality, so will it be in its elimination and 

 regainment of its pristine vigour. 



The relations of the several reciprocal unions in the above 

 tables is another point which we must briefly consider, as having 

 most important bearings on the subject of oar present enquiry. A 

 hasty examination suffices to show that these are much complica- 

 ted. Thus V. lychinitis, lutea, in its two unions with the white and 

 yellow varieties of V. blattaria, the heterochromatic unions are the 

 more fertile ; whereas in its two unions with the white and yellow 

 varieties of V. thapsus, we find it yields the more fertile by 

 a homochromatic union. Again V. blattaria, lutea, in its four 

 distinct unions with the white and yellow varieties of V. thapsus 

 and V. lychnitis, yields the higher degree of fertility in the hete- 

 rochromatic unions, while the V. blattaria in its similar unions with 

 the white and yellow varieties of V. thapsus and lychnitis is, 

 singularly enough, more highly fertile in the homochromatic than the 

 heterochromatic unions. Lastly the V. thapsus, lutea, yields more 

 seed by its heterochromatic unions with pollen of the V. lychnitis, 

 alba, than by its homochromatic unions with the V. lychnitis, lutea ; 

 whereas in the converse unions we have seen that the V. lychnitis, 

 lutea, is more fertile in the homochromatic unions with V. thapsus, 

 lutea, than in the heterochromatic unions with V. thapsus, alba ! 



The tabulated experiments given in C. 3, afford another source of 

 complexity to the question under examination, inasmuch as they are 

 quite irregular in the relative degree of fertility produced by 

 the affinity of colour. Thus by the three unions of V. lychnitis, 

 lutea, with pollen of the three varieties of V. phoeniceum, the 

 most highly fertile is that in which V. lychnitis r lutea, is treat- 



