124 Heredity. 



to an unusual degree. Now, if our theory of heredity is 

 true, if the seminal fluid is especially adapted for the 

 transmission of gem mules, while their transmission by an 

 ovum is a matter of accident, the tendency to yary must 

 be transmitted by the male hybrid. 



When children are born from two hybrid parents it is 

 impossible to show that the variability which follows 

 comes from the father rather than from the mother, but 

 the subject can be put to a test by crossing the male hybrid 

 with a female of one of the pure species, and the male of 

 one of the pure species with the female hybrid. Neither 

 pure species has any especial tendency to transmit vari- 

 ation, while the male hybrid has such a tendency. If, 

 then, we cross the female hybrid with the male of 

 one of the pure forms, the offspring would not be ex- 

 pected to be unusually yariable; but if the male hybrid 

 is crossed with one of the pure females we should expect 

 the offspring to be unusually yariable. 



Now it is very interesting to find that this actually is 

 the case. Thus Gartner states (Bastarderzengnng, p. 

 452, 507) that when the seeds of Dianthus barbatus were 

 fertilized by the pollen of the hybrid Dianthus chinensi- 

 barbatus, the seedlings were more yariable than those 

 which were raised from the seeds of the hybrid fertilized 

 with the pollen of Dianthus barbatus. Darwin states 

 that Max Wichura obtained the same result with wil- 

 lows. Gartner concludes from a number of experiments 

 that when a hybrid is used as the father, and either 

 one of the pure parent species or a third species as the 

 mother, the offspring are more yariable than when the 

 same hybrid is used as the mother, and cither pure par- 

 ent or the third species as the father. 



Darwin's pangenesis hypothesis furnishes no explana- 

 tion whatever of this curious fact. On the contrary, as 



