110 THE ORIGIN OF GYNANDROMORPHS. 



actual vascular connection between the two individuals. There can 

 remain no doubt that the results are due to the estabhshment of a 

 common circulation. Lillie brings very strong evidence in favor of the 

 view that the freemartin starts as a normal female. The failure of 

 her ovary to develop, he thinks, is due to a sex hormone (see below) 

 that originates in the testis of the male and suppresses the normal 

 development of the ovary. The external genitalia of the freemartin, 

 and to some extent the uterus and ducts, are, as a rule, less affected by 

 the hormone, so that externally the freemartin appears to be a female. 

 Even more remarkable is the fact that the male ducts are sometimes 

 quite well developed and the development of the ovary appears to 

 take in somewhat the characteristic changes seen in the development 

 of the testis. This conclusion is based largely on the results of a histo- 

 logical examination by Miss C. L. Chapin. Lillie is not inclined, how- 

 ever, to lay very much emphasis on this side of the question, because, 

 as he states, the suppression of the ova (and female stroma?) may in 

 itself allow some of the male characteristics to develop to a stage not 

 normally present in the female. In other words, the development of 

 the accessory organs may to a certain extent be under the influence of 

 the gonad. 



The assumption of a male hormone originating in the interstitial 

 cells of the testis is more problematical. The only fact advanced by 

 Lillie in favor of this interpretation is that in the testis the interstitial 

 tissue develops at an earlier stage than that in the ovary. It is true 

 that there is also some evidence indicating that the interstitial cells of 

 the testis produce some substance that affects the secondary sexual 

 characters of the male. But it may be that other substances in the 

 blood of the male affect the ovary of the freemartin and retard its 

 development. Such substances might also be called hormones, but 

 have no direct relation either to the development of the germ-cells 

 in the testes or to sex determination in any specific sense. If in cattle 

 the male differs from the female by one sex chromosome, it is quite 

 possible that the composition of the blood of the male is different in 

 some substances (or relative proportion of substances) from the blood of 

 the female. The difference, while the product of sex in the sense 

 that all the body-cells of the male differ by one chromosome from the 

 body-cells of the females, might not in any way be connected with 

 sex determination, even although it affected injuriously the develop- 

 ment of the ovary of the young female embryo. Until further evidence 

 is obtained, the source of the "hormone" that affects the freemartin 

 must remain an open question. 



If the ovary of the freemartin is actually changed to a testis it may 

 be said that the freemartin is a sex mosaic, the external genitalia female 

 and the gonads more or less male. The cause of such a sex mosaic 

 would, then, obviously, be entirely different from the cause of the 

 gynandromorphs of Drosophila. 



