574 EXPERIMENT STATION EECORD. [Vol. ?.8 



The biology of twins, H. H. Newman (Chicago: Univ. Chicago Press, 1917, 

 pp. JX+186, pi. 1, figs. 55).— In this book the attempt has been made to gather 

 from various sources the facts about mammalian twins and to unify these 

 varied situations into one point of view. A detailed account is given of the 

 facts revealed by the study of monozygotic twinning in the armadillo, as, in 

 the author's opinion, this is the nearest approach at present possible to the 

 direct study of twinning in mammals, and more especially of human twinning. 

 The phenomenon of freemartinism in cattle is reviewed and its bearings on 

 the problems of sex biology noted. The study of twins in relation to the fol- 

 lowing problems is discussed: (1) Tlie time of and the mechanics of sex- 

 determination, (2) the significance of sex-ratios, (3) the mechanism of sex- 

 differentiation, (4) the inheritance of twinning, (5) modes of inheritance in 

 monozygotic or poly embryonic twins, and (6) the nature and significance of 

 symmetry reversals in monozygotic twins. 



A mule and a horse as twins, and the inheritance of twinning, \V. R. B. 

 ROJ3ERTSON (Kans. Univ. Sci. BuL, 10 (1917), No. 15, pp. 293-298, pis. 4).— The 

 author presents data in reference to the birth of a female mule and a male 

 horse as twins. The year previous to the birth of these twins their dam, just 

 10 minutes before being bi'ed to a jack, had been bred to a 3-year-old stallion. 

 It is noted that this mare in the nine times she had produced foals had given 

 birth to twins (mules) on two other occasions. In addition one of her single 

 mare foals had produced twins (horses), and also her own half sister had 

 produced twins. The inheritance of color in the twin offspring of this mare is 

 discussed. Photographs of the mare and the mule-and-horse twins are 

 reproduced. 



Some breeding statistics, R. Beanfobd (Agi: Jour. India, 12 (1917), No. 4, 

 pp. 573-578). — Brief notes are given on color inheritance in mules, asses, sheep, 

 and cattle and sex ratios in cattle and asses. The data were obtained for the 

 most part from breeding operations at the Government cattle farm at Hissar, 

 India. 



Receipts and shipments of live stock, 1916 (Union Stock Yard and Transit 

 Co. Chicago, Ann. Live Stock Rpt., 51 (1916), pp. 3-56). — This gives the re- 

 ceipts and shipments of live stock at the Union Stock Yards, Chicago, for 1916, 

 with a summary of receipts and shipments and valuations of all live stock for 

 a term of 51 years ended December 30, 1916. 



Live stock slaughtered (Joitr. Agr. [New Zeal.], 15 (1917), No. 2, p. 110).— 

 The following stock was slaughtered in New Zealand during the year ended 

 March 31, 1917: Cattle, 328,708; calves, 19,396; sheep, 3,341,910; lambs, 

 3,411,621 ; and swine, 153,444. This showed an increase over the previous year 

 of 20,403 head of cattle, and a decrease of 389,733 sheep, 653,479 lambs, 14,374 

 calves, and 16,271 swine. 



Indo-China live stock; exports to France and the Far East, C. Sarazin 

 (Bui. Econ. Indocliine, n. ser., 19 (1916), No. 121, pp. 563-608). — A discussion 

 of the live-stock industry in Indo-China with statistics of exports. The needs 

 of the industry are discussed and methods proposed whereby it may be bettered 

 and enlarged. 



Inheritance of fertility in Southdown sheep, E. N. Wentworth and J. B. 

 Sweet (Amer. Nat., 51 (1917), No. 611, pp. 662-682).— The authors review the 

 literature on inheritance of fertility in sheep and give results of a biometrical 

 study of data obtained from flockbooks of the Southdown, Shropshire, Dorset, 

 and Cotswold breeds. 



It Is concluded that " in general sheep of a high birth rank tend to produce 

 offspring of a high birth rank. On the basis of the few data presented the 



