ov4 Ewarr-— Variation: Germinal and Environmental. 
particular environment, but in both cases there will be danger from the “‘ swamping 
effects of intercrossing.” ‘This danger will obviously be avoided if, when the new 
and old varieties intercross, the offspring are either the image of the old or of the 
new. If, in addition to an inability to produce intermediate forms, the new variety 
is better adapted for the environment, it will survive even if its increase is at first 
slow. 
4. The offspring may combine, almost unimpaired, the more striking characters 
of both breeds. Though the engrafting of the characters of one breed on another 
may not be common, it certainly occurs. ‘Two instances may be mentioned: 
(1) In crossing a barb with an ‘ owl,” the frill of the owl on two separate occasions 
made its appearance on the offspring, one of which, from a fancier’s point of 
view, was, apart from its frill, a better barb than its pure-bred barb parent ; 
(2) In crossing a home-made Himalaya rabbit with an Angora, two young were 
obtained, having the long hair of the Angora and the dark markings of the 
Himalaya. That it is possible to roll two races or breeds into one is extremely 
interesting and suggestive. Darwin supposed that when two distinctive types 
were crossed, reversion followed from a kind of antagonism, 7.e. from the germ-plasm 
of one type opposing and neutralizing the germ-plasm of the other. What 
happens when intercrossing is practised evidently largely depends on the pre- 
potency of the parents, or, to be more accurate, on the prepotency of the germ- 
cells lodged in the parents. This prepotency may again depend partly on the 
inheritance, and partly on the environment from the outset of development up to 
the time when maturity is well established. When the characters of one race are 
engrafted on those of another, it is not, I believe, because there is an absence 
of antagonism ; it is rather that in both germ-cells there is almost sufficient energy 
to give rise, unaided, to a new individual. The Skewbald pony producing a foal 
as like herself as if it had grown from a cutting or bud, supports this view, but 
still stronger support is afforded by the recent work of Yves Delage,* who has 
succeeded in obtaining larval echinoderms, worms, and molluscs by fertilizing 
enucleated eggs. If in nature, two distinct types occasionally blend, it will be 
evident that the rate of evolution, even without the help of occasional “ sports” 
may have been infinitely more rapid than Darwin and many of his followers 
imagined. If the blending of external characters is possible, it may almost be 
taken for granted that the blending of mental characters is also possible. I find 
when my zebra hybrids are intensely striped, they exhibit practically all the 
mental traits of their zebra sire. This might, perhaps, have been anticipated, for 
the epidermis and its appendages and the central nervous system are akin in their 
origin. Hence, from the fact that distinctive epidermic characters of one variety 
of pigeons can be engrafted on quite a different variety, it may be inferred that, 
* Archives de Zoologie Expérimentale, Oct., 1899. 
