19181 ANIMAL PRODUCTION. 169 



turing them for 210.3 days. The total cost of maintaining a beef cow in the 

 Shorthorn lot was .$33.54, and in the Aberdeen-Angus lot, .$34.11. 



The breeding results of the experiment indicated that the most important 

 single factor for success in profitable beef production was regularity of the 

 cows in producing calves. Under the conditions of the experiment, 70 per 

 cent calves cost ,$49.73 and had a market value of .$50.40, while 80 per cent 

 calves were produced at 6.1 cts. per pound. 



The period of gestation was 285 days in both lots. In lot 1 the calves averaged 

 75.27 lbs. at birth and 671.6 lbs. at twelve months of age, while the heifers at 

 twenty-four months of age averaged 991.6 lbs. In lot 2 the calves averaged 

 68.36 lbs. at birth and 588.8 lbs. at twelve months, while the heifers at twenty- 

 four months of age averaged 905 lbs. The number of services per pregnancy 

 in lot 1 was 1.63 times and in lot 2, 1.43 times. 



Heifers at thirty months of age for breeding purposes cost less than their 

 market value as beef. The steers were of better grade tlian steers purcliased 

 for ft'Cding purposes by tlie college in the fall of 1913 and co.sting 7.45 cts. per 

 pound when placed in the feed lot. 



The investigation indicates that beef production can be made profitable 

 under present Pennsylvania conditions where the breeding herd is maintained 

 largely on roughage during the winter and on pasture during the siunmer, when 

 cattle of insured beef type are used, and when more than 70 per cent calves are 

 rai.sed annually. 



Shorthorn cattle, A. H. Sanders (Chicago: Sanders Publishinf/ Co., 1916. 

 pp. 840, pis. 61, figs. S). — This book is a very comprehensive treatise on the 

 origin and development of the Shorthorn breed of cattle, and their introduction, 

 progress, and future in the United States. 



Twinning in cattle, with special reference to the free martin, L. J, Cole 

 (Abs. in Science, n. scr., JfS (1916), No. 1101, pp. 177, 178).— A .study of .303 

 multiple births in cattle showed 43 cases as homosexual male, 105 cases recorded 

 as heterosexual (male and female), 88 cases as homosexual female, and 7 

 cases of triplets, a ratio of twins of approximately 1:4:2, instead of the 

 expected 1:2:1. The expectation is brought more nearly into harmony with 

 the facts by assuming that in addition to ordinary fraternal (dizygotic) twins, 

 there are numbers of " identical " (monozygotic) twins of both sexes, and that 

 while in the case of females these are both normal, in the case of a dividing 

 male zygote to form two individuals in one of them the sexual organs remain 

 in the undifferentiated stage, so that the animal superficially resembles a female 

 and is ordinarily recorded as such, although it is barren. The records for 

 monozygotic twins accordingly go to increase the homosexual female and the 

 heterosexual classes, while the homosexual male class, in which part of them 

 really belong, does not receive any increment. 



The theory of the free martin, F. R. Lillie (Science, n. set:, 43 (1916), No. 

 1113, pp. 611-613). — A preliminary report of embryological investigations of 

 the subject in which the author takes exception to the theory supported by Cole 

 (see above) that the sterile free martin is really a male cozygotic with its mate. 



An anatomical classification of 41 cases of bovine twins, all examined in 

 utero, gave a ratio of 145 5 : 21 5 9 : 69 $. It is concluded from the examina- 

 tion of these 41 cases that about 97.5 per cent of bovine twins are monochorial, 

 but in spite of this nearly all are dizygotic. In cattle a twin pregnancy is 

 almost always a result of the fertilization of an ovum from each ovary. The 

 rapid elongating ova meet and fuse and the blood vessels of the two circula- 

 tions anastomose 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 



