612 



SCIENCE 



[N. S. Vol. XLHI. No. 1113 



give licfc? : 21c?? : 6??. It will be observed that 

 this agrees with expectation to the extent that 

 the sum of the homosexual classes is (almost) 

 equal to the heterosexual class; and it differs 

 from expectation inasmuch as the c^c? class is 

 over twice the S2 class instead of being equal to 

 it, as it should be if males and females are pro- 

 duced in equal numbers in cattle. The mate- 

 rial can not be weighted statistically because 

 every uterus containing twins below a certain 

 size from a certain slaughter house is sent to 

 me for examination without being opened. 

 Cole's material shows twice as many female 

 as male pairs, and the heterosexual class is 

 about one third greater than the sum of the 

 two homosexual classes. I strongly suspect 

 that it is weighted statistically ; the possibility 

 of this must be admitted, for the records are 

 assembled from a great number of breeders. 

 But, whether this is so or not, if we add the 

 sterile free-martin pairs of my collection to the 

 male side in accordance with Cole's suggestion, 

 we get the ratio 32c?d' : 3c?$ : 65$, which is ab- 

 surd. And if we take Cole's figures, divide his 

 heterosexual class into pairs containing sterile 

 females and pairs containing normal females 

 according to the expectation, 6 of the former 

 to 1 of the latter, and add the former to his 

 male class, we get an almost equally absurd 

 result (184(?c?:23c?2:882S). On the main 

 question our statistical results are sufficiently 

 alike to show that the free-martin can not pos- 

 sibly be interpreted as a male. The theory of 

 Spiegelberg, D. Berry Hart, Bateson and Cole 

 falls on the statistical side alone. 



But the real test of the theory must come 

 from the embryological side. If the sterile 

 free-martin and its bull-mate are monozygotic, 

 they should be included within a single 

 chorion, and there should be but a single 

 corpus luteum present. If they are dizygotic, 

 we might expect two separate chorions and two 

 corpora lutea. The monochorial condition 

 would not, however, be a conclusive test of 

 monozygotic origin, for two chorions originally 

 independent might fuse secondarily. The facts 

 as determined from examination of 41 cases 

 are that about 97.5 per cent, of bovine twins 

 are monochorial, but in spite of this nearly all 



are dizygotic; for in all cases in which the 

 ovaries were present with the uterus a corpus 

 luteum was present in each ovary; in normal 

 single pregnancies in cattle there is never more 

 than one corpus luteum present. There was 

 one homosexual case (males) in which only 

 one ovary was present with the uterus when 

 received, and it contained no corpus luteum. 

 This case was probably monozygotic. 



There is space only for a statement of the 

 conclusions drawn from a study of these 

 cases, and of normal pregnancies. In cattle a 

 twin pregnancy is almost always a result of 

 the fertilization of an ovum from each ovary; 

 development begins separately in each horn 

 of the uterus. The rapidly elongating ova 

 meet and fuse in the small body of the uterus 

 at some time between the 10 mm. and the 20 

 mm. stage. The blood vessels from each side 

 then anastomose in the connecting part of the 

 chorion; a particularly wide arterial anasto- 

 mosis develops, so that either fetus can be 

 injected from the other. The arterial circula- 

 tion of each also overlaps the venous territory 

 of the other, so that a constant interchange of 

 blood takes place. If both are males or both 

 are females no harm results from this; but if 

 one is male and the other female, the repro- 

 ductive system of the female is largely sup- 

 pressed, and certain m,ale organs even develop 

 in the female. This is unquestionably to he 

 interpreted as a case of hormone action. It is 

 not yet determined whether the invariable re- 

 sult of sterilization of the female at the ex- 

 pense of the male is due to more precocious 

 development of the male hormones, or to a 

 certain natural dominance of male over female 

 hormones. 



The results are analogous to Steinaeh's 

 feminization of male rats and masculinization 

 of females by heterosexual transplantation of 

 gonads into castrated infantile specimens. 

 But they are more extensive in many respects 

 on account of the incomparably earlier onset 

 of the hormone action. In the case of the free- 

 martin, nature has performed an experiment of 

 surpassing interest. 



Bateson states that sterile free-martins are 

 found also in sheep, but rarely. In the four 



