HYBRIDS 95 



sire, the zebra. Matopo.* There are other experiments 

 recounted which tell the other way, and at present this 

 matter remains in a state of considerable uncertainty. 

 Further experiment may probably show that though 

 in most cases the oldest type is likely to prevail, the 

 offspring may take after the most inbred of its parents. 

 The matter is not altogether as simple as the above 

 statements would imply. For instance, a sport is often 

 strongly prepotent. Standfuss's experiments in hybri- 

 dizing butterflies tend to show this, and Mr. Galton 

 even looks upon prepotency as a sport or an aberrant 

 variation. These butterfly experiments also indicate 

 that the male is usually prepotent over the female ; 

 but so many questions of nutrition, the maturity of 

 the germ-cells, etc., enter into these intricate problems 

 that it is exceedingly difficult to disentangle the several 

 factors which play a part in the constitution of every 

 living being. 



Some years ago it used to be taught that species 

 are infertile inter se ; nowadays it almost seems that 

 we are giving up the idea of species altogether. No 

 two naturalists take precisely the same view of what 

 constitutes a species, and no one has succeeded in 

 defining shortly and clearly what a species is. The 

 intersterility test has broken down ; the common goose 

 and the Chinese goose, the common duck and the 

 pintail duck, various species of pheasant, the ox of 

 Europe and the American bison or the Indian zebu, 

 not only breed together, but yield hybrids which are 

 themselves fertile ; and the same is true of many 

 plants. Why the hybrids of Equidae should prove 

 sterile is not clear. 



This article must not close without a word or two 



* The illustration shows the difference between the facial 

 marks of the zebra and those of the hybrid. The latter, in 

 this respect, bears much the same relation to the former as a 

 blue-rock pigeon does to a fancy type. 



