Hybrids and their Phenomena. 123 



into bold relief by merely reporting the circum- 

 stances of successful hybridation, or the crossing of 

 species. In the first place, it is man's interference 

 that brings it about. Nature does not affect it; 

 though there are some native instances reported in 

 almost every order. M. Suchetet sums them up 

 in an exhaustive article on the subject, in the num- 

 ber for last July of the Revue mentioned before. 

 Secondly, hybrids are rare. As to their number in 

 the state of nature, considering that there are 

 143,000 species classified among animals by zoolo- 

 gists, the facts of hybridism which are reported from 

 every quarter and through every channel, " might 

 be multiplied," says the same authority, "ten times 

 over without acquiring any importance in the ques- 

 tion. " So they are fare. Thirdly, they are sterile, 

 as is well known in the case of the mule, which is 

 the commonest and most uniformly successful ex- 

 periment of hybridation. It is narrated that Arab 

 populations, which ought to be better acquainted 

 with the natural facts of horse, ass and mule than 

 any other people, have been thrown at times into 

 the depths of superstitious dread by the report cir- 

 culating that a mule had been productive. Fourth- 

 ly, however, hybrids have maintained themselves 

 for some time in a line of descent; and elaborate 

 experiments with animals and plants have shown 

 the phenomena that now come into play. It re- 

 quires extraordinary care to maintain them at all. 

 In spite of the care, some of the offspring at each 



