THE DARWINIAN HYPOTHESIS 119 



prejudice should fail to stir the mind, one learned coleop- 

 terist will fill ten attractive volumes with descriptions of 

 species of beetles, nine-tenths of which are immediately 

 declared by his brother beetle-mongers to be no species 

 at all. 



The truth is that the number of distinguishable living 

 creatures almost surpasses imagination. At least a hundred 

 thousand such kinds of insects alone have been described 

 and may be identified in collections, and the number of 

 separable kinds of living things is under estimated at 

 half a million. Seeing that most of these obvious kinds 

 have their accidental varieties, and that they often shade 

 into others by imperceptible degrees, it may well be imagined 

 that the task of distinguishing between what is permanent 

 and what fleeting, what is a species and what a mere 

 variety, is sufficiently formidable. 



But is it not possible to apply a test whereby a true 

 species may be known from a mere variety ? Is there no 

 criterion of species ? Great authorities affirm that there 

 is that the unions of members of the same species are 

 always fertile, while those of distinct species are either 

 sterile, or their offspring, called hybrids, are so. It is 

 affirmed not only that this is an experimental fact, but 

 that it is a provision for the preservation of the purity of 

 species. Such a criterion as this would be invaluable ; 

 but, unfortunately, not only is it not obvious how to apply 

 it in the great majority of cases in which its aid is needed, 

 but its general validity is stoutly denied. The Hon. and 

 Rev. Mr. Herbert, a most trustworthy authority, not only 

 asserts as the result of his own observations and experiments 

 that many hybrids are quite as fertile as the parent species, 

 but he goes so far as to assert that the particular plant 

 Crinum capense is much more fertile when crossed by a 

 distinct species than when fertilised by its proper pollen 1 

 On the other hand the famous Gaertner, though he took 

 the greatest pains to cross the primrose and cowslip, 

 succeeded only once or twice in several years ; and yet it 

 is a well-established fact that the primrose and the cowslip 

 are only varieties of the same kind of plant. Again, such 

 cases as the following are well established. The female 

 of species A if crossed with the male of species B is fertile, 

 but if the female of B is crossed with the male of A, she 

 remains barren. Facts of this kind destroy the value ol 

 the supposed criterion. 



