198 THE BREEDING OF ANIMALS^ 



500 pounds of butter in one year. Some individuals 

 are very fertile, others may be sterile or markedly deficient 

 in this very desirable quality. 



189. Meristic variation. All plants or animals develop 

 in accordance with a certain symmetrical pattern. A 

 quadruped has four legs, two ears, two eyes, and two sides 

 of similar character. A deviation from the characteristic 

 plan or pattern of the species is called a meristic variation. 

 Such variations are of very great importance among 

 plants, but are of little practical significance to the animal- 

 breeder. Examples of meristic variation are to be seen 

 in the doubling of flowers, the stooling of grains, and 

 the production of four-leaved clovers. Among animals 

 the growth of extra fingers and toes, and the development 

 of an abnormal number of vertebrae or ribs, are not un- 

 common. .An interesting example of this type of varia- 

 tion is found in the development of extra mammae. 

 Supernumerary nipples in mammals are a common form 

 of variation among humans. Bruce 1 found fourteen 

 cases of extra mammae among 2311 females examined. 

 Most male mammals are supplied with rudimentary 

 nipples, and curiously there seems a greater amount of 

 variation among males than females. The same authority 

 quoted above found forty-seven cases of multiple nipples 

 among 1645 males examined. In one case a woman 2 

 is reported to have possessed five pairs of nipples. The 

 presence of a larger number of mammae than the normal 

 has been regarded by some as evidence of greater fertility. 3 

 A variation in the opposite direction resulting in the 

 development of a smaller number of digits than the normal 



1 Bateson, "Materials for the Study of Variation." 



2 Ibid., p. 183. 



3 Bell, "Multinippled Sheep." 



