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THE AMERICAN NATURALIST [Vol. L 



ciently large to maintain the race. 6 On the contrary, any theory 

 of ontogeny or phylogeny which demands the existence of a 

 mechanism to provide an embryo pig with the particular num- 

 ber of nipples which would agree closely with the number of 

 young she may be destined to bear as an adult would seem to be 

 not merely cumbersome, but unnecessarily teleological. Since 

 male pigs have more mammas than females, the cost to the organ- 

 ism is apparently not prohibitive ! What one should expect as 

 the result of the action of natural selection would, therefore, not 

 be the development of a regulative mechanism to provide the 

 mother with a number of nipples in close agreement with the size 

 of her future brood, but the development of a number of nipples 

 sufficiently large for the needs of the race. 



Pearl's own data show only 7 out of 57 "disadvantageous" 

 combinations, and the table as it stands takes no account of early 

 deaths. 7 Furthermore, his series is small, only 57 individuals, 

 and apparently hardly typical of swine as a class. Parker and 

 Bullard on the basis of a thousand litters show that the (em- 

 pirical) modal number of nipples is twice the modal number of 

 young, and that the average number of nipples is much more 

 nearly twice the number of young than in Pearl's short series. 

 Thus the data of both Pearl and Parker and Bullard indicate in 

 the words of the latter authors that "disadvantageous combina- 

 tions in which the number of young pigs outrun the provision for 



« Natural selection can not be expected to accomplish more for the de- 



of development necessary for the survivafof the species in competition with 

 others. That correlation between the number of the young and the number 

 of nipples is not necessary under conditions of domestication is shown by 

 the classic observations of Minot on the guinea pig (Jour. Phys., 12: 103, 

 1891) in which he pointed out that in his studies 143 litters showed a 

 variation of from 1 to 8 in the number per litter, with a model frequency on 

 2 and an average of 2.5, although the number of developed mammae is two. 



That the number of young born may regularly exceed the number of 

 nipples in a species persisting under natural conditions is shown by the 



, 59: 133-173, 1914) in wl 

 it of eggs are discharged : 



possii.iy survive because of the limited accommodation of the i 

 newborn' 41111 ** 617 tn,Stwortl ! y figures showin g directly the mortality of 

 tality is considerable is indicated by certain of the figures' given for another 

 purpose by Eward. 



