296 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Hermaphroditism in Toads.* — 0. Fuhruiann examined 91 male 

 toads in the month of April, and found that 11 were in some degree 

 hermaphrodite. There may be slight hermaphroditism in the gonads 

 or in the ducts, or there may be potentially, if not also effectively, 

 functional autogamy. 



Reproductive Organs of Free-martin.f — D. Berry Hart discusses 

 the nature of a free-martin, which is an apparent sterile twin cow, usually 

 co-twin with a potent bull. It has, in this case, the lower part of its 

 genital tract to the naked eye like that of a cow, the upper part defective, 

 and it is usually considered as a cow sterile from incomplete develop- 

 ment of its upper vaginal and uterine tract. The author dealt with thirty 

 recorded cases and with John Hunter's specimens, and finds that the 

 free-martin, when the co-twin is a potent male, is a sterile male, and not 

 a sterile female, i.e. they are identical male twins, except in their genital 

 tract and secondary sexual characters. There is no trace of ova, the 

 gonads are testes, and an epididymis is present. The potent and sterile 

 twins arise from one zygote : " the somatic determinants are equally 

 divided, the genital determinants unequally divided, the potent going to 

 the one twin, the potent bull, the non-potent genital determinants to the 

 free-martin." The potent organs are dominant, the non-potent reces- 

 sive, and a Mendelian interpretation is possible. The free-martin is a 

 pure or extracted recessive qua its genital determinants, and the potent 

 twin a pure or extracted dominant. 



Leuco-reaction in Pregnancy.! — Ch. Achard, Henri Benard, and 

 Ch. Gagneux find that during pregnancy the leucocytes react in a specific 

 way to placental extract. A study of the leuco-reactions makes it 

 possible to determine the stage of pregnancy. There is also a placental 

 reaction in the new-born (but not after a few days) and in sexually 

 mature males. 



Influence of Male Parent in Heredity. § — Gustave Loisel has experi- 

 mented for five years on rabbits (288), carefully measuring all the 

 organs in each generation. His general conclusion is that the male 

 parent not only determines the characters of a proportion of the progeny, 

 but modifies, in a degree which seems to be measurable, the hereditary 

 transmission of the recessive characters of the grandparents. 



Use of Selection Index Numbers in Breeding. || — Raymond Pearl 

 and Frank M. Surface call attention to the usefulness of " selection 

 index numbers " in breeding operations. The idea of such index num- 

 bers is to combine in a single numerical expression the values of a series 

 of variable characters with regard to all of which the breeder wishes to 

 practise selection at the same time. The analytical expression of this 

 idea is discussed, and its adaptability and usefulness are illustrated by 

 examples drawn from poultry and maize breeding. It is shown that 

 selection index numbers form a valuable adjunct to the score card in 

 stock judging. 



* Arch. Sci. Phys. Nat., xxviii. (1909) pp. 499-500. 



t Proc. Roy. Soc. Edinburgh, xxx. (1910) pp. 230-41 (2 pis.). 



X C.R. Soc. Biol. Paris., lxviii. (1910) pp. 159-01 (1 fig.). 



§ Tom. cit., pp. 153-6. || Amer. Nat., xliii. (1909) pp. 385-400 (1 fig.). 



