ANIMAL PRODUCTION. 267 



It is stated that " experience seems to warrant the expectation that in later 

 generations, after there has been time for selection, there may be seen on 

 caltaloes having say 10 per cent or less of bison blood, as good fur as is now 

 seen on the half and three-quarter buffaloes." There is also some prospect of im- 

 proving the beef carcass by this hybridizing, for the bison carries an exceedingly 

 high percentage of beef on the back, and the inheritance of this quality may be 

 encouraged by selection. While there was some irregularity in the fertility of 

 the hybrids it is believed that both males and females will be fairly fertile, and 

 that complete fertility if not found at once will doubtless come through selec- 

 tion, as will early maturity. 



Sex determination in sheep, compiled by P. B. Popenoe (Jour. Heredity, 5 

 (1914), yo. 2, pp. JfG-o7. flrjs. Jf). — Observations were made by A. G. Bell on his 

 flock on Cape Breton Island during 1899-1001 on the effect of nourishment of 

 the mother on the sex of offspring and on the production of twins. Earlier 

 observations had led to the conclusion that " three conditions favorable to the 

 production of twins revealed themselves: (1) Maturity in the ewes (ewes 

 4. 5, and 6 years old yielding a larger percentage of twins than younger or 

 older ewes). (2) mating in October (with consequent lambing in March), 

 and (3) a rapid increase of weight at the time of mating with subsequent loss 

 of weight." 



The results obtained in 1899 were inconclusive as to whether the extra feed- 

 ing given the ewes in the fall had caused them to produce a larger percentage 

 of twins than ordinary. However, it is noted that " no less than 72 per cent 

 of the March-born lambs were females — a circumstance quite unprecedented 

 jji the history of the flock." 



Believing that possibly climatic conditions were involved, an inquiry was 

 made as to the flocks on the whole island of Cape Breton, the result of which 

 showed that there had been a majority of males. The female percentage was 

 therefore a local matter. Data were then collected as to the treatment during 

 the preceding year of one flock which had produced 88.5 per cent males. 

 Mating occurred at a time when the ewes were beginning to lose weight, after 

 which they remained in reduced condition until their lambs were born. These 

 results were in contrast to those obtained with, the experimental flock and seemed 

 to indicate that si)ecial feeding in the fall may have been responsible for the 

 large proportion of females born in 1900. A study of the weight of the ewes 

 shows that " at the beginning of October, before mating had been accomplished, 

 the average weights of the two classes of ewes (male-bearing and female- 

 bearing) were the same. The average male-bearing ewe increased in weight 

 up to the end of October, after which there was a decline ; the average female- 

 bearing ewe, on the other hand, continued to gain in weight all through Novem- 

 ber so that by the end of that month the average female-bearing ewe outweighed 

 the male-bearing — a superiority retained during the subsequent decline." 

 Similar observations had been noted in earlier trials, 1890-1899. 



It was further observed that the mothers of twins were above the average of 

 the flock in weight and the mothers of single lambs were below the average. 

 "Among the twin-bearing ewes there were none who had male lambs exclu- 

 sively. Those which had male as well as female lambs were losing in weight 

 at the time of mating and immediately after; whereas those which had female 

 lambs alone were increasing in weight at the time of mating, and, though the 

 weight dropped afterwards, did not continue to drop but remained substantially 

 on a level for several weeks." It was found that the mothers of males were 

 losing in weight at the time of mating, whereas the mothers of females retained 

 their weight. From these observations it is concluded that " variations of 

 weight occurring at or about the time of mating may have great significance. 



