212 COOK 



selection might have, it is true, no tendency to render such a 

 conjugate character transmissible, but the chance that gametes 

 might be found which tended to the same expression as the con- 

 jugates might warrant such an effort if the heterozygote charac- 

 ter was sufficiently valuable. 



Whether any heteroz3rgote characters represent really new 

 variations seems not to have been definitely ascertained. In 

 case they should all prove to be in the nature of reversions this 

 method of descent will coincide with the next. 



Conjugate Reversion. — Conjugate reversion is a form of de- 

 scent in which the conjugates become different from both of the 

 parent organisms by returning to the expression of an ancestral 

 character of one or both of the parents. Thus Darbishire re- 

 ports that numerous crosses of two varieties of pink-eyed mice 

 yielded only black-eyed offspring in the first or conjugate 

 generation. 



Perjugate Reversion. — Perjugate reversion is a method of 

 descent in which the conjugates do not depart from the charac- 

 ters of the parents, but the perjugates become abruptly different 

 by returning to the expression of an ancestral character. Per- 

 jugate reversion differs from conjugate reversion in that the an- 

 cestral character reappears in the perjugate generation, instead 

 of in the conjugate generation. 



Perjugate reversion may be illustrated by an experiment 

 reported by Dr. Herbert J. Webber. The crossing of Sea 

 Island cotton with a smooth-seeded Upland variety resulted in a 

 conjugate generation which was smooth-seeded like the parents, 

 but in the second or perjugate generation woolly seeds reap- 

 peared, and for several generations afterward.^ 



Both kinds of reversion may be considered as due to a restora- 



' " Where the smooth-seeded Klondike upland was used in crossing with Sea 

 Island the second generation hybrids exhibited a very peculiar case of reversion. 

 The Klondyke, while originally a fuzzy-seeded type, had been carefully selected 

 for a number of generations before the crossing was done, until it produced regu- 

 larly and normally a smooth black seed. When crossed with Sea Island the first 

 generation hybrids all had smooth black seeds. In the second generation, how- 

 ever, quite a number of the progeny had fuzzy seed, showing that the fuzzy seed 

 potent still existed in the Klondike though dormant. This would seem to be an 

 important point, as indicating the non-purity of the germ-cell." Webber, H. J., 

 1905. Cotton Breeding. Proc. Amer. Breeders' Association, i: 40. 



