TRIPI.ET CALVES. 265 



The relation between primary and secondary sexual character 

 in these free-martins obviously presents a problem of consider- 

 able interest. 



4. Cases of multiple gestation present two interesting prob- 

 lems in inheritance. One of these concerns the degree to which 

 a tendency toward multiple gestation in a normally uniparous 

 form may be inherited. Are the o^fFspring of a mother having 

 this tendency likely to show it also? Comparatively little 

 detailed work has been done upon this subject though a gen- 

 eral impression appears to prevail that such tendencies are 

 inherited. Thus Wilder'" says regarding one particular sort of 

 multiple gestation, viz., the production of duplicate twins. 

 (loc. cit. p. 368:) "As the tendency to produce duplicate 

 twins and other sorts of abnormal cosmobia seems inherent in 

 certain organisms, and to be transmitted by heredity., it is quite 

 possible that we may be able to breed certain of the viable 

 forms." 



There have been a few detailed studies on the inheritance of 

 the tendency towards multiple pregnancies. In man Weinberg" 

 and Oliver'^ have recently investigated the influence of heredi- 

 ty on twin bearing. Weinberg's paper is by far the most 

 thorough study of the subject which has yet appeared. From 

 a careful analysis of copious statistics he concludes that the 

 tendency towards multiple pregnancies is inherited in Alendelian 

 fashion, this character apparently behaving as a recessive. He 

 regards heredity as having a greater influence in the production 

 of multiple gestation than any other one factor. It was foun3 

 impossible to account satisfactorily for the facts on the assump- 

 tion of blending inheritance. While any single external factor 

 certainly has less influence than heredity in causing multiple 

 gestation, still the sum total of all such external influences must 

 outweigh heredity in affecting observed variations in the num- 

 outweigh heredity in bringing about observed variations in the 



"Wilder, H. H. The Morphology of Cosmobia; Speculations con- 

 cerning the Significance of Certain Types of Monsters. Amer. Jour, 

 of Anat., Vol. 8, pp. 355-440, 1908. 



"Weinberg, W. Die Anlage zur Mehrlingsgeburt beim Menschen 

 und ihre Vererbung. Arch. f. Rass. u. Gesellsch. Biol. Bd. 6, pp. 322- 

 339, 470-482, 609-630. 1909. 



^^Oliver, James. The Hereditary Tendency to Twinning, with some 

 Observations concerning the Theory of Heredity generally. Part I. 

 Eugenics Rev. Vol. IV, pp. 39-53, 1912. 



