GENERAL INTRODUCTION. XXXlll 



membered that Eomanes in describing telegony says^ " It 

 is so rare that I doubt whether it takes place in more 

 than 1 or 2 per cent, of cases;" adding, however, that 

 ''nearly all my professional correspondents would deem this 

 an absurdly low estimate." Evidently, should the fact 

 of telegony be proved, it will be necessary to determine 

 as accurately as possible whether it is a very rare or a 

 comparatively common phenomenon. 



5. DucJis.- — Another interesting case of reversion may 

 be mentioned. A cross between a common wild duck 

 and a black Cayuga di-ake produced during the present 

 summer to a common wild drake seventeen ducklings. 

 Of these nine are like the black Cayuga grandsire, while 

 eight take after the wild drake — the immediate sire.* 



6. Horses. — I may here mention several instances of 

 apparent reversion in the Equidte. 



(a) Teeth. — The ancestors of the horse had seven cheek 

 teeth — four premolars and three molars — on each side of 

 the upper jaw. The recent horse has, as a rule, only 

 three (2 — 4) premolars. When a fourth (the wolf-tooth) 

 is present it is small, and usually soon disappears. In 

 zebras there are often four premolars in the upper jaw, 

 and the first is sometimes nearly as lai-ge as in the extinct 

 three-toed horse Hipparion. Two years ago I bred a bay 

 Shetland foal, having several distinct stripes on the neck 

 and shoulders, bars in the vicinity of the "knees" and 

 hocks, and, in addition, a distinct dorsal band. In this 

 foal the first premolar (wolf-tooth) was large — relatively 

 nearly as large as in Hipparion. 



(6) Digits.- — The biologist is as satisfied that the horse 

 has descended from five-toed ancestors as the astronomer 

 is that the earth moves round the sun, and he knows that 

 not very long ago, geologically speaking, all horses had 

 three complete digits encased in three separate hoofs. 

 The digits borne by the fore-limb corresponded to the 

 fore, middle, and ring fingers in man, the hind digits to 

 our three middle toes. As I pointed out some years ago, 



* To Alexander Cowan, Esq., of Woodslee, Penycuik, I am indebted 

 for the information about tlie ducks, and for various other friendly deeds. 



