264 MAINE AGRICUI^TURAI, EXPERIMENT STATION. I912. 



viduals born as twins, for example, exhibited the same distribu- 

 tion in respect to sex as do random pairs of individuals born 

 singly, it would be expected that twins would show the follow- 

 ing sex relations. 



Sex of twins: $S c^S $? 



Frequency of occurrence : n : 2n : n 



Actually multiple births in man and the domestic mammals 

 show nothing of the kind. For example, Nichols \loc. cit.) 

 gives the following figures for human twins. 



Sex of twins : c^d* c?? " ?? 



Observed frequency of occurrence : 234,497 : 264,098 : 219,312 



Expected frequency if the distribu- 

 tion of sex within the pair was a 

 random one: 179,476.75 : 358.953-SO : 179,476.75 



A discussion of this curious phenomenon of sex distribution 

 will, be published in a later paper. 



In addition to such disturbances of the sex ratio there also 

 occur in connection with multiple gestation cases of apparently 

 incomplete sex determination, such as those leading" to the 

 production of so-called "free-martins." 



3. Mention has been made of free-martins. Not only do 

 these animals furnish interesting data in regard to the deter- 

 mination of primary but also of secondary sexual characters. 

 In many cases free-martins have been considered to be herma- 

 phrodites, on the basis of their external appearance. In other 

 cases such individuals are notably ferhinine in their characteris- 

 tics, so much so indeed as to be used for show or demonstra- 

 tion purposes because they are so typical of the females of the 

 race. 



A classical example of this kind is found in the Short Horn 

 breed in the case of the famous "White Heifer that Trav- 

 elled." " 



Tor an account of this animal see Sanders, A. H., "Short-Horn 

 Cattle." Second Edition, Chicago, 1901, pp. 41 and 42. This account 

 is evidently copied, almost verbatim, from that given in Allen, L. F., 

 "History of the Short-Horn Cattle. Their Origin, Progress and Pres- 

 ent Conditions." Buffalo, (publ. by the Author). 1872. p. 52. This 

 "white heifer," which was widely exhibited about 1806 as a typical 

 specimen of the breed, was a free-martin. She was one of a pair of 

 twins of which the other was a bull, and she herself did not breed. She 

 was a very heavy animal, her weig'ht at slaughtering having been esti- 

 mated to be not less than 2300 lbs. The picture of this "White Heifer" 

 given by Sanders {loc. cit.), presumably copied from some contem- 

 porary print, shows her to have been typically feminine in appearance. 

 This agrees with the statements regarding this specimen which have 

 come down to us. 



