152 On the Reproductive Functional [No. 3, 



these eggs from hybrid birds breeding inter se have failed to produce 

 young, not from absolute sterility, but sterility in degree, from an 

 amount of vitalization insufficient to carry out the whole result of 

 reproduction, in which the young individual has been completed, 

 leaving it with vital resistance insufficient to maintain life and cope 

 with common and customary external influences." And thus in those 

 curious cases of sterility of structurally hermaphrodite organisms, 

 whose sexual elements have become differentiated with respect to their 

 mutual fertile conjunctions, so in the phenomena of sterility from 

 hybridism, we find, as Mr. Salter well remarks, with respect to the 

 relations of hybridism and parthenogenesis, "that the sterility is not 

 absolute but in degree, and that the stimulus, whatever it may be, 

 which starts the embryonic changes is feeble and imperfect rather 

 than wholly wanting." 



I have now shown that a regular more or less early embryonic abortion 

 results from the self-fertilisation of certain individual plants of V. 

 l)lioeniceum and vars. roseum, and album ; whereas by their reciprocal 

 fertilisation, highly fertile unions may in general be effected. By again 

 consulting Table 1, however, it will be seen that besides a reciprocal 

 fertilisation, these three plants are also susceptible of fertilisation by 

 pollen of other species. Thus in lines 7, 8, 9, of Table 1, the male 

 element of V. nigrum is singularly enough effective in the fertilisation 

 of each, while in a succeeding Table — 4 — the goodness of the male 

 elements is also similarly shown by each effectively fertilising the 

 female element of the V. lychnitis, lutea. Again, we have fuller illus- 

 trations of these curious sexual phenomena in Table 2, in which one 

 of the above plants, V. phoeniceum, yields a varying degree of fertility 

 to four other distinct species ; namely the V. ferrugineum, Blattana 

 lutea and alba ; Lychnitis lutea and ovalifolia. These are indeed 

 remarkable physiological revelations. How strange that an individual 

 plant could be fertilised by the pollen of five distinct species, and yet 

 not by its own good pollen : how singular also, as shown above, to see 

 three hermaphrodite individuals incapable of self-fertilisation, yet 

 having each sexual element reciprocally meeting and fertilising the 

 opposite elements of other species. Thus, for example, the male 

 element of V. phoeniceum and vars. roseum and album fertilise the 

 female element of V. lychnitis } while the female elements of the three 



