24 INHERITANCE. Chap. XIIL 



pletely separate. How this is possible, and what the term 

 specific essence or element may be supposed to express, I shall 

 attempt to show in the chapter on the hypothesis of pangenesis. 



But Naudin's view, as propounded by him, is not applicable 

 to the reappearance of characters lost long ago by variation ; 

 and it is hardly applicable to races or species which, after 

 having been crossed at some former period with a distinct 

 form, and having since lost all traces of the cross, neverthe- 

 less occasionally yield an individual which reverts (as in the 

 case of the great-great-grandchild of the pointer Sappho) to 

 the crossing form. The most simple case of reversion, name! 3^, 

 of a hybrid or mongrel to its grandparents, is connected by an 

 almost perfect series with the extreme case of a purely-bred 

 race recovering characters which had been lost during many 

 ages ; and we are thus led to infer that all the cases must be 

 related by some common bond. 



Gartner believed that only highly sterile hybrid plants ex- 

 hibit any tendency to reversion to their parent-forms. This 

 erroneous belief iiiaj perhaps be accounted for by the nature 

 of the genera crossed by him, for he admits that the tendency 

 dijBfers in different genera. The statement is also directly con- 

 tradicted by Naudin's observations, and by the notorious fact 

 that perfectl}^ fertile mongrels exhibit the tendency in a high 

 degree, — even in a higher degree, according to Gartner 

 himself, than hybrids. ^^ 



Gartner further states that reversions rarely occur with 

 hybrid plants raised from species which have not been culti- 

 vated, whilst, with those which have been long cultivated, 

 they are of frequent occurrence. This conclusion explains 

 a curious discrepancy : Max Wichura,^^ who worked exclu- 

 sively on willows which had not been subjected to culture, 

 never saw an instance of reversion ; and he goes so far as to 

 suspect that the careful Gartner had not suflicientl}^ protected 

 his hybrids from the pollen of the parent-species : Naudin, on 

 the other hand, who chiefly experimented on cucurbitaceous and 

 other cultivated plants, insists more strenuously than any other 



** ' Bastarderzeugung,' s. 582, 438, der Weiden,' 1865, s. 23. For Gartner's 

 &c. remarks on this head, see 'Bastard- 



*2 ' Die Bastardbefruchtuug . . . erzeugung,' s. 474, 582. 



