244 



DISCOVERY 



undertook an inquiry upon this subject and accumu- 

 lated a quantity of statistical evidence extending over 

 three years for flocks of Black-faced, Cheviot, Border 

 Leicester, and cross-bred sheep. The records collected 

 clearly showed that sheep which were fed upon oats_ 

 maize, dried grains, or turnips or other additional food 

 at the time when the rams were turned out to the ewes 

 and for about three weeks previously, but which were 

 maintained upon grass only for the greater part of 

 the year, had a better crop of lambs than sheep which 

 were not subjected to such treatment. The percentage 

 of twin lambs born was very perceptibly increased. 

 Merely putting ewes upon superior pasture for a short 

 time before " tupping," and without any special 

 feeding, was often sufficient to increase the fertility 

 of the flock. Among " flushed " flocks of Border 

 Leicester or half-bred Border Leicester ewes the number 

 of lambs per ewes was nearly 200 per cent., while for 

 sheep of the same breeds which were not so treated 

 the average proportion of lambs per ewes was between 

 150 and 160 per cent. The best condition for the 

 breeding ewes was a good thriving or "improving" 

 one, an excess of fat being as detrimental to fertility 

 as a too lean condition. The effect of the practice of 

 " flushing " or nutritive stimulation is clearly to 

 increase the number of ova discharged at a time. 

 Once the process of discharge is accomplished, no 

 amount of extra feeding can increase the number 

 of developing young, for this number is determined 

 at the time of " tupping." An adverse circumstance 

 during the period of gestation may reduce the crop of 

 lambs, but favourable conditions at this season can do 

 nothing to increase it if a sufficiency of mature ova 

 has not previously been produced. 



Influence of Male Parent 



It is thus seen that in a certain sense the female 

 parent is often a more important factor in fertility 

 than the male, since the female usually controls the size 

 of the litter. There is, however, another sense in 

 which the male parent may be regarded as the more 

 important factor. It is usual for a good stallion to 

 mate with eighty or more mares in a season, and for 

 a ram to mate with about fifty ewes. It is obvious, 

 therefore, that any failure in the power of procreation 

 on the part of the male parent may cause temporary 

 sterility in a large number of females, and such an 

 effect is by no means an unknown occurrence. Again, 

 it has been sometimes found that a female who is 

 barren with one male will be fertile with another. 

 Thus Dorset Horn ewes, which fail to breed when put 

 with a Dorset Horn ram, may subsequently produce 

 lambs after mating with a Hampshire Down ram. 

 Furthermore, Mr. John Hammond, of Cambridge, has 

 shown that with sows the activity of the female 



generative gland may outstrip the capacity of the 

 animal to produce fully developed piglings, and that 

 a certain number of these may die and degenerate 

 before being born. The cause of this phenomenon is 

 still under investigation, but it seems probable that 

 it is a question of nutrition. 



Inheritance of Fecundity 



Fecundity, like other characteristics, may be 

 hereditary, and some breeds are notoriously more 

 fertile than others. Thus among sheep the Dorset 

 Horns are far more prolific than sheep belonging to 

 hill breeds, even though the latter are bred amid 

 lowland conditions. Moreover, by breeding from sheep 

 which were twins the fertility of a flock may be 

 increased, and the capacity to bear twins can be trans- 

 mitted through the ram to the next generation of ewes 

 of which that ram was sire in just the same kind of way 

 as the deep-milking propensity of some cows may be 

 transmitted through the bull to the next generation of 

 female calves. So also Pearl has shown that the 

 capacity to lay an increased number of eggs possessed 

 by some strains of fowls may be transmitted through 

 the cock. 



Among the Stars 



An Astronomical Commentary 



The Total Eclipse of September 10 



The astronomical event of the month will be the 

 total eclipse of the Sun on September 10. The 

 shadow of the Moon will strike the Earth's surface in 

 the North Pacific Ocean, just off the coast of Asia. It 

 will then cross the Pacific, traversing the American 

 continent by way of California and Mexico and ending 

 in the Atlantic, just off the northern coast of South 

 America. As the eclipse will be the most favourable 

 visible on American territory for over twenty years, it 

 will be extensively observed, and numerous expeditions 

 are being fitted out by the various American observa- 

 tories. The Lick astronomers will be stationed at 

 Ensenada, and the Mount Wilson observers at San 

 Diego, while the Yerkes Observatory station will be on 

 Catalina Island. 



In recent eclipses, the chief object of observation has 

 been to subject the Einstein theory of relativity to 

 observational tests. In view of the results attained 

 last year, however, this question may now be regarded 

 as settled in favour of the theory, and accordingly 

 other problems which in recent years have fallen into 

 the background will come in for their share of atten- 



