THROUGH CUMULATIVE SEGREGATION. 
265 
grandchildren any advantage over the self-fertilized grandchildren 
raised from the self-fertilized children.” “ And, wliat is far 
more remarkable, the great-grandchildren, raised by crossing the 
grandchildren with a fresh stock, had no advantage over either 
the intercrossed or the self-fertilized great-grandchildren. It 
thus appears that Hero and its descendants differed in consti- 
tution in an extraordinary manner from ordinary plants of the 
same species.” “ If we look to the [ordinary] plants of the ninth 
generation in table x., we find that the intercrossed plants [of 
the same stock] were in height to the self-fertilized as 100 to 79, 
and in fertility as 100 to 26 ; whilst the Colchester-crossed 
plants [raised by crossing with a fresh stock] were in height to 
the intercrossed as 100 to 78, and in fertility as 100 to 51.”* 
The Colchester-crossed plants were therefore in height to the 
self-fertilized as 1 to '78 x '79, or as 1000 to 616, and in fertility 
as 1 to *51 X '26, or as 1000 to 133 ; while the self-fertilized 
descendants of Hero when crossed with the same fresh stock 
not only had no advantage over those that had been continuously 
self-fertilized for nine generations, but, as the details of the 
experiment show, the advantage was on the side of the plants 
raised from the self-fertilized seed. The experiment was con- 
ducted under conditions decidedly unfavourable for the production 
of healthy plants ; but, as it is usually found that the superiority 
of crosses between varieties is most clearly brought to light when 
the competitors are subjected to unfavourable circumstances, it 
seems to furnish even stronger evidence of Segregate Vigour 
being occasionally produced in the earliest stages of divergent 
evolution, than would have been furnished if the same degree of 
superiority in the self-fertilized plants had been obtained under 
a less severe test. As the case is of unusual interest, I give the 
details as recorded by Darwin : — 
“ Several flowers on the self-fertilized grandchildren of Hero 
in table xvi. were fertilized with pollen from the same flower ; 
and the seedlings raised from them (great-grandchildren of 
Hero) formed the ninth self-fertilized generation. Several other 
flowers were crossed with pollen from another grandchild, so 
that they may be considered as the offspring of brothers and 
sisters, and the seedlings thus raised may be called the inter- 
crossed great-grandchildren. And, lastly, other flowers were 
fertilized with pollen from a distinct stock, and the seedlings 
* ‘ Cross- and Self-Fertilization,’ pp. 47, 60, 61. 
