On the offspring of rabbit-does mated with two sires simultaneously
The possibility of fecundation of several eggs of one female by two different sires during one rutting period has been methodically ascertained.
Heterogeneous foetuses derived from such successful double mating, i.e. developing simultaneously, may manifest their respective colour as well as that of their offspring in total independence from each other.
If there exists an essential difference in the weight of rabbits from two different breeds, the difference may manifest itself even when the heterogeneous rabbits develop simultaneously in one doe. On the other hand, the presence of foetuses of different breeds in one mother may cause an essential positive influence on the weight of new-borns belonging to either type. This positive influence can, however, not be detected in the first filial generation from such enlarged specimens.
The increase of weight of new-borns from double mating ought to be considered as modification in the sense given by Baur. It is possibly due to the introduction of certain substances characteristic of foetuses of one type, into the surroundings, or even into the interior of those of the other type.