NATURAL SELECTION 85 



are large enough for Natural Selection to take notice of; as to 

 the latter, we have to prove that though they appear in isolated 

 cases, sporadically here and there, yet they are not swamped by 

 inter-crossing. Taking the large variations first, we find many 

 examples of a sire or dam having a strong prepotency so that 

 a marked characteristic, though found in one parent only, re- 

 appears unreduced in the offspring. 



I have a fan-tail pigeon which has paired with a homer. 

 Many of the young have little trace of the fan-tail about them, 

 but in colour and contour of plumage follow the mother. In 

 some cases, when a white traveller has had children by a woman 

 of colour, his descendants of several generations have reproduced 

 his characteristics, though there has been no second recourse to a 

 white strain. "In 1791, a ram lamb was born in Massachusetts, 

 having short crooked legs and a long tail like a turn-spit dog. 

 From this one lamb the otter or ancon semi-monstrous breed was 

 raised ; as these sheep could not leap over the fences, it was 

 thought that they would be valuable ; but they have been sup- 

 planted by merinos and thus exterminated. These sheep are 

 remarkable for transmitting their character so truly that Colonel 

 Humphreys never heard of but one questionable case of an ancon 

 ram and ewe not producing ancon offspring. When they are 

 crossed with other breeds, the offspring, 'with rare exceptions, 

 perfectly resemble either parent" * 



Darwin quotes also the case of the birth of a merino ram, 

 " remarkable for its long, smooth, straight and silky wool." 

 From this a number of sheep having the same characteristics 

 were raised. " The first ram and his immediate offspring were 

 of small size, with large heads, long necks, narrow chests and 

 long flanks ; but these blemishes were removed by judicious 

 crosses and selection." 2 



It is evident, then, that strikingly large variations appearing 

 in one individual may be perpetuated, and that the aphorism 

 natura non facit saltum is not of universal application. It is im- 

 portant to recognise this, since it shortens the time required 



1 Darwin, "Animals and Plants under domestication," vol. i., p. 100. 



2 Darwin, loc. cit., see also The Penycuik Experiments, by Prof. J. C. Ewart. 



