Some Recent Work on Hybrids in Plants, 77 
mixed nature by their offspring. By a study of the next generation 
it was found that, similarly, the hybrids of the second generation 
produced offspring of which only half were hybrids, the others 
being pure forms exhibiting the dominant and recessive character 
in equal numbers. A study of further generations produced by 
self-fertilisation gave exactly similar results. 
If A be taken to represent the dominant character, and a the 
recessive, then Aa represents the case in which the two are combined, 
and A -f 2 Aa -f A will represent in proper relative proportion the 
three classes of forms in the progeny of either the original or later 
hybrids produced by crossing races bearing the differentiating 
characters A and a. It is clear that as only half the offspring of 
the hybrids of one generation are hybrids in the next the number of 
hybrids will in a few generations become a very small proportion of 
the total progeny of any given hybrid. The gradual dying out of 
the hybrid character confirms the observations of Gartner, Kolreuter 
and others, that hybrids are inclined lo revert to their parental 
forms. 
The accompanying table shows at a glance the numerical 
relation of the various classes into which the offspring of a single 
hybrid fall in the first few generations, each plant being supposed 
to bear only 4 fertile seeds. The terms A and a are used as above. 
The forms Aa and A are of course externally indistinguishable. 
PARENTS. 
HYBRID AND OFFSPRING. 
I. Gen. 
II. Gen. 
III. Gen. 
IV. Gen. 
V. Gell. 
A 
> 
1 A ... 
4 a ... 
16 A ... 
64 a 
2 A ... 
8 A ... 
32 a 
4 A ... 
16 A 
I 
j 
8 A 
Aa 
k 
2 Aa 
\ 
4 A a }> 
8 A a 
16 A A 
1 
1 
J 
8 A 
J 
4 A ... 
16 A 
y 
2 A ... 
8 A .. 
32 A 
A 
1 A ... 
4 A ... 
IGA ... 
64 A 
It is clear that in such a scheme in the fifth generation there 
are only sixteen hybrids out of a total progeny of 256 . The 
proportion of the three classes a, Aa and A is 15 : 2:15 in this 
generation. Further a general formula can be obtained showing 
that in the next generation the relative number in the three classes 
is 2 n ~ I —1 : 2 : 2 n l —1. 
The phenomena describe! in relation to the offspring of the 
