472 EXPERIMENT STATION KECOKD. 



ANIMAL PRODUCTION. 



The causation of sex, E. K. Dawson (London. 1909, pi>. 196; rev. in 8ci. 

 I'rou. Ticcntivth Cent.. ', (1909). \o. 13, pp. 1G5. liU]; Anirr. Nnt., .'/.} (1909), 

 Xo. 516, pp. 756-762). — The aim of the author of this hook is to preseTit ovi- 

 dence based on clinical material to show that sex is determined in the unfer- 

 tilized ovum; that in the human species, and perhaps in all mammals, the 

 female-bearing eggs are produced only in tli(> left ovary and male-bearing in the 

 right ovary because the weaker sex must be derived from the ovary of the 

 weaker side; and that ovulation takes place alternately from right to left ovary. 



The secret of sex, E. Jl. Dawson (Neto Yorlc. 1909, pp. 6), pi. 1). — An 

 abridged edition of the worlv noted above. 



The causation of sex, II. PI Jordan (Atncr. Nat., J/S (1009), No. 516, pp. 

 7-')(j-762). — This is a review and criticism of the views outlined in tlie boolv noted 

 above. It is pointed out that well-known facts established by researches in 

 i-ytologj' and comparative embryology are left out of account in Dawson's 

 theory of sex determination and that thei'e are numerous exceptions to the 

 clinical evidence presented. " By the same methods it would probably be as 

 easy to prove the reverse position, tliat is, that females come from the right 

 ovary and males from the left." 



Mendelian action on differentiated sex, I). B. Hart ( I'roc. Roy. Snr. Edinb., 

 29 (1908-9), Nos. 6, pp. 607, 608; 7, pp. 609-618, figs. 3; abs. in Jour. Roy Micros. 

 Boc. [London^, 1909, No. 6, pp. 703-705). — An inquiry into the origin of sex 

 gametes with especial reference to the Mendelian theory of sex inheritance. 



The author thinks that gametes originate, not from the germ or sperm 

 epithelium, but fi-om the primitive germ-cell, a generalization wliich he calls the 

 Owen-Weissmann law. Ovarian and testicular teratomata are considered to 

 be i)arts of embryos originating from primitive germ cells wliich have been 

 reduced to gametes but which liave retained in part tlie power of zymotic 

 development not normally possessed by a gamete except by union with another 

 gamete. 



The author concludes that the liuman zygote is an impure dominant of Fi in 

 Mendel's scheme and that the dominant and recessive determinants do not 

 segregate normally, hence in the twinning of one zygote we always get an equal 

 division of sex determinants. It is pointed out, liowever, that this is not the 

 case with some animals, as in cattle. According to this view the free-martin 

 is not a sterile cow when the potent twin is a bull, but a sterile bull with the 

 recessive sexual determinants segregated in it, tliat is, an extracted recessive. 

 Concerning the sex of bees, it is stated that the view of the origin of the drone, 

 a perfect male from an unfertilized egg, is neither a fact nor a theory, but a 

 reductio ad absurdum. 



A bibliography of the literature of tlie subject is appended. 

 [The law of ancestral heredity], E. Davenport (Breeder's Gaz., 56 (1909), 

 Nos. 25, pp. 136S, 1369; 26, pp. I'i2'i, 1J,25 ; 57 (1910), No. 1, pp. 16, 17).— A series 

 of articles which discuss the similarity between parent and offspring and the 

 importance of Galton's ancestral law for breeding operations. 



The studies of Gallon on human stature, and those of Kietz on the inheritance 

 of milk fat production, previously noted ( E. 8. 11., 22, p. 27S), are used to illus- 

 trate the law that though there may be no close reseud)lance between an indi- 

 vidual and its immediate parent a study of large numbers will show that there 

 is a resemblance between an indiviilual and its total ancestry. Parents produce 

 a great variety of olfspring and in those from exceptional parents there is a 

 strong tendency toward mediocrity. To prevent undesirable regression accurate 

 records must be kept of animals used for breeding puri)Oses. At present there 



