, 
CANNON: Stupres in Prant Hyprips 141 
These may be the heterozygotes,* and consequently cannot breed 
true or be fixed by selection. Such birds bred together, give many 
plain heads and birds with coarse crests.’’ 
Bateson also speaks of the relation of other phenomena to the 
Mendelian conception, such as continuous or discontinuous variation, 
Prepotency and the determination of sex, but it will not be necessary 
in this connection to quote more at length. 
Although the foregoing account of the relation of the history 
of hybridizing to that of the other biological sciences is from 
necessity an outline only, I think it can be seen that hybridiza- 
tion has at various times played an important rdle, and occasionally 
a definitive one, in aiding the solution of perplexing biological 
problems. 
THe ReEsutts OF EXPERIMENTAL HYBRIDIZATION 
Florists and gardeners have long employed the crossing of 
closely related plants + as a means of obtaining new and useful 
races and it is without doubt largely due to them that so much is 
at present known about the behavior of plant hybrids. To the 
practical as well as to the theoretical hybridizer the manner of the 
transmission of the parental characters, the fertility or sterility of 
the hybrid, and the variation of the hybrid race are of the highest 
importance. 
The variation in hybrids is dependent on the manner in which 
they reproduce parental characters. These characters may be 
blended in the hybrid, they may be associated in a variety of ways, 
or the hybrid may recapitulate in detail the characters of either par- 
ent. Moreover, the hybrid of the primary cross may show variation 
toa different degree from that of the second, or of the later genera- 
tions. The phenemona in the first generation are the essentials 
of what is commonly understood by the term hybrid, and as such 
are described in all literature of the subject ; the behavior of the 
hybrids in the second and following generations, although of the 
greatest importance, has been little studied. 
ie Reena dominant, but 
* By ‘heterozygote’? is evidently meant a hybrid, apparently aes Paarlings’’ of 
really with both opposing characters (‘allelomorphs ”” of ey mis Se ac 
Correns ) united to fors the “zygote” ; in the “ homozygotes,’’ on the other han 
characters of the pair are alike. : , 
+ Compare Richard Bradley's “New Improvements of Planting and Gardening, 
both Philosophical and Practical,’’ p. 16. London, 1726. 
