1S99.] Pe7iycuik Experiments. 117 



Hitherto stock-breeders have worked on rather haphazard lines, and 

 there can be no doubt that they will greatly benefit b) r the application 

 of thoroughly scientific methods to their experiments. 



From the older experiments conducted by Darwin and others, we 

 know already that the crossing of extreme forms appears to lead to 

 reversion towards a remote ancestor, and also that some breeds are more 

 prepotent than others. Reversion, again, thinks the author, " seems to 

 lead to a form of rejuvenescence due presumably to the ancestral units 

 overcoming and controlling the more recently evolved and less stable 

 units, which, if allowed to have their way, would give rise to offspring 

 bearing all the marks of decadence that characterised the immediate 

 ancestors." 



What, then, do we understand by prepotency ? The author's explana- 

 tion clearly indicates to us what is meant by the term: "Any animal, 

 male or female, which strongly impresses its own peculiarities of form, 

 colour, disposition, &c, on its offspring is prepotent, while animals that 

 are the offspring of more or less intimately related parents are inbred — 

 when the parents have been closely relate'd for several generations they 

 are said to be grossly inbred." " The wild parent is said to be especially 

 prepotent because it belongs to an older and longer established type 

 than our domestic breeds." 



As for inbreeding, it is a subject we know little about. It appears that 

 artificial prepotency may be gradually produced by it by fixing the 

 characters of the particular variety of stock selected. On the other hand, 

 intercrossing ma) 7 arrest the deleterious effects of inbreeding. 



Discussing the supposed decadence of the English race-horse, the 

 author states that, in his opinion, the best way to maintain its speed, 

 staying power, and constitution would be to have recourse occasionally 

 to Australia or New Zealand for sires and dams equal, if possible, in 

 fiettness and size to our own thoroughbreds, but differing from them in 

 having a recent dash of Arab blood in their veins. 



Perhaps the most interesting parts of Prof. E wart's experiments are 

 those connected with the subject of " telegony." This term, it may be 

 mentioned, is applied to the supposed permanent influence by the first 

 male on the offspring of a female with which it had been mated. So 

 far, however, the author s experiments give no support to the telegony 

 hypothesis. 



After a perusal of Prof. Ewart's beautifully illustrated work, we clearly 

 perceive the intricacies underlying the principles of breeding. The 

 author has by no means solved the many problems connected with the 

 subject, but he has shown us that the methods of scientific inquiry can 

 be of much practical use to the breeder. He has also indicated to us the 

 manner in which future experiments should be conducted, and altogether 

 has given to us a work of great interest from a biological point of view. 



R. F. S. 



