IDENTICAL TWINS FROM JAPAN 



Yeiichi and Yuji Ogata, of Toyko, at the age of 168 days. Yuji, on the right, is only 30 minutes 

 older than his brother. The father of these twins, a member of the American Genetic- 

 Association and himself a twin, states that even the parents have difficulty in distinguish- 

 ing one from the other. There is no record of twins in the mother's ancestry. Such cases 

 as this are commonly believed to lend support to the view that the tendency for identical 

 twinning is transmitted as readily by the male as l^y the female. (Fig. 2.) 



C. H. Danforth, St. Louis, Mo. 



mains a neuter, although determined as 

 a male. An analogous operation on 

 females produces analogous results. 

 Steinach, in a brillant series of experi- 

 ments with rats, has shown that a 

 transplantation of ovaries into a young 

 castrated male markedly alters its sex- 

 differentiation, making it take on many 

 characters of the female; even milk 

 glands become functional and a maternal 

 instinct develops. The con\'erse opera- 

 tion on a female tends to masculinize 

 her ; she becomes large like the male and 

 exhibits the pugnacious character of the 

 latter. Since only the glandular por- 

 tion of the transplanted ovary or testis 

 survives in these experiments there is 

 no alternative but to attribute the re- 



versal of sex-tendency to some secre- 

 tion of these glands, and, for lack of a 

 better term, the active principle has 

 been called hormone. These hormones 

 must be given off into the blood, for they 

 affect all parts of the body. 



Crucial as are the experiments in 

 transplantation of glands, they do not 

 equal in subtlety and finish the experi- 

 ment of nature performed in the case of 

 the freemartin. Here an individual 

 genetically determined to be a female 

 may become more or less completely 

 differentiated into a male by the very 

 neat device of borrowing hormone- 

 charged blood from its male co-twin. 



These results make it necessary to 

 distinguish most carefully between sex- 



247 



