374 ■ FRANK R. LILLIE 



association with a male in utero is, therefore, in some way a 

 necessary condition of the phenomenon. It is also an invari- 

 able rule that the male tmn is normal; the reverse condition of 

 a normal female with a defective male probably does not occur. 

 All of my own cases were found in association with a normal bull 

 twin; in the other possible twin combinations both individuals 

 are normal. Of course genital abnormalities may occur apart 

 from tmnning, so that the possibility exists that in a sufficiently 

 large collection of twins an individual might be found with geni- 

 tal abnormaUties not due to its association with a twin. In this 

 connection Numan ('44) notes that malformation of the sexual 

 organs causing infertility had not yet been observed in single born 

 heifers in his experience; but, in single born males, individuals 

 with incomplete formation of the organs of reproduction had 



female similar to one of my own cases (no. 44), and hence no exception; it is 

 discussed in extenso, p. 413 of the present paper. 



Numan also states, "In two-sexed twins the malformation is not confined 

 exclusively to the heifer; but may also occur in the case of the bull, in which case 

 the heifer is normal. However such examples appear to be very rare." This also 

 refers to a single case viz., that of a two year old bull sent him by a veterinarian 

 who stated that it had been born twin to a female. According to the veterinarian 

 there was not the least abnormality discernible in the external organs of the 

 heifer; the internal anatomy was not studied. The bull exhibited a hypo- 

 spadiac condition; it possessed a split scrotum and the testes were in the abdom- 

 inal cavity against the inguinal rings. Numan himself points out that such 

 abnormalities are not rare in l)ulls born single. Since the actual condition of the 

 female twin was not known, and the condition in the bull is a rather common 

 anomaly the evidence is entirely inadequate to support the idea that the con- 

 dition was due to twinning. 



Numan's emphasis of these doubtful cases appears to be due in part to his 

 fundamental objection to considering free-martins as hermaphrodites. He 

 classified them therefore either as females or as males with defective organs of 

 reproduction; in two-sexed twins the female was classified as male if the modi- 

 fication of the reproductive organs proceeded beyond a certain degree, thus 

 establishing in his mind the occurrence of a profound genital anomaly in one 

 individual of exceptional male pairs; this seemed to render probable a similar 

 occurrence in the opposite case of female twins, which may seem to account for 

 liis uncritical acceptance of the case cited above, and his equally uncritical 

 interpretation of modification of the bull as due to twinning with a female. 



The entire basis for Numan's statements concerning exceptions to the rule is 

 untrustworthy, and the exceptions cannot be accepted seeing that they are 

 supported by no other writers. 



