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THE AMERICAN NATURALIST [Vol. XLVII 



although the determination of the pair as a Mendelizing 

 unit must be deferred until further study is made. 



Rudimentaries in the Abdominal Series. — Bateson looks 

 on rudimentaries that occur asymmetrically in the ab- 

 dominal series of mammae, as a sort of supernumerary 

 organ systematically and different qualitatively from the 

 normal mammas. He so classifies them because of their 

 visible differences and because of their ability to displace 

 normal mammae from the ordinary paired state. It seems 

 to the writer that while this distinction may be all right 

 from Bateson 's standpoint, from the standpoint of hered- 

 ity it is without weight. The factor that causes the trans- 

 verse sectioning of the strips of mammary tissue is 

 obviously separate from the forces that cause develop- 

 ment of the glands. This factor operates irrespective of 

 whether the gland be destined to develop or not, and it is 

 very evidently this factor (probably complex) that is 

 inherited. 



At birth or shortly after it is difficult to tell whether a 

 mamma will develop functionally or not. There are some 

 that are so small and undeveloped that one may be posi- 

 tive as to their rudimentary state throughout life, but 

 there are others for which prediction is very uncertain. 

 The writer has left all doubtful cases out of consideration 

 and has figured asymmetry due to a rudimentary nipple 

 in relation to asymmetry produced by developed teats. 



There are 89 asymmetrical males. One of these is 

 asymmetrical from the presence of a rudimentary; two 

 more possess a rudimentary each, but are asymmetrical 

 through the presence of functional "triangles"; and two 

 symmetrical boars possess rudimentaries as one member 

 of a pair. It must be understood in connection with the 

 foregoing that all of the mammae of the male are really 

 rudimentary, and that what the writer has termed rudi- 

 mentary in the preceding statement refers to mammae 

 that are so much smaller as to occupy a relation similar 

 to the rudimentary and normal mammae in the young 

 female. 



