STOCK AND BREEDING.

New Zealand Herald, Volume LXIV, Issue 19808, 1 December 1927, Page 18

STOCK AND BREEDING.

BY H.B.T.

CLAWS OF REPRODUCTION. PRE-DETERMINATION OF SEX. THEORIES AND BELIEFS*

Many of the vital problems connected ■\with animal reproduction are as little runderstood as when the Patriarchs first interested themselves in their flocks and fcerds. We have learned that in microscopic cells are contained ail the characteristics end peculiarities of the iemale, as well ik? the inherited characteristics of her iforebears lor many generations. These •-female cells at conception are, we Iknow, blended with an equal number of unale cells having a similar variety of Tito result of such a iblend of diverse traits is that nature mever produces two oi anything m tiie .animal world that are exactly alike. .Similar, they may be, to the extent that it is hard to detect a difference, but the difference is always there, an improvement or a retrogression -in so far as the animal'q service to man is concerned, and the man who, through close study and observation of Ins charges can detect and appraise the value ol these " differences " is he who harnesses the law of evolution to his own and the world's gain. This variation is the foundation of evolution. Through variations, both in the vegetable and animal world, lite adapts itself to its surroundings until perfect harmony between the two exists. Should the conditions surrounding any form of life alter materially, those animals or plants which have not the characteristic of adaptability cease to exist and a new type or breed is evolved which bring into prominence in their offspring the characteristics which made survival of <lie jparents possible. Controlled Evolution. This is selective breeding or evolution liin nature which produces new types and .'breeds. The successful breeder of live [Stock is he who realises tho possibilities .and at the same time the limitations of Jhis country and its climate, and by intelligent selection and mating uses evolution to produce an animal suited to its environment yet as valuable as possible to man. While scientists have traced hereditary ■characteristics back to the' minute cells in which life starts, and in some instances can tell us which particular cell controls oi ? holds within it tho possibilities of development of a particular ■organ or characteristic in the adult animal, they are as yet unable to tell ■ns what it is that imparts life to these cells.

Many theories have been ' formulated, amd in tests some have appeared to give a measure of control. Thus one scientist contended that sex is dependent on the maturity or " ripeness " of the female cells or ovum at the time of conception. If impregnation occurs early in a period he ttays the result is a female, while if it occurs toward the end of the period the result will surely be a male. This is known as " Thury's Law," and was propounded by Professor Thury, a veterinary surgeon of K.e Academy of Geneva, Switzerland. A number of stock raisers, both in Europe and America, claim to have tested this " discovery," and their -evidence sems to be generally, though not entirely, confirmatory. Cross-Heredity of Sex. Another theory that has received considerable support is that known as "Cross-Heredity of Sex." According to this theory the physically and constitutionally stronger party in the mating tends to reproduce its opposite. Thus, ■where the male is more healthy and stronger than the female, the offspring is female; males predominating where the female has a stronger grip on life. Hippocrates and others of his time held that males were produced when both par ents were extremely vigorous and healthy, ■while females resulted from parents of lower vitality

Again 1 read in a farm journal only a few days ago the assertion of a farmer that ho could control the sex of his farm progeny by temporarily tiring one or other of the parents immediately prior to mating The cow that was driven a con siderable distance before being mated "almost always" bore a heifer, while •when the bull was tired the result was a anale. Present Theories All Disproved. Every one ot these theories has been disproved, even though some appear to have an influence on the determination of sex. That sex is not a matter of chance has, however, been proved to the satisfaction of most investigators, but nature apparently persists in producing, under normal conditions, approximately fiftyfifty. Some animal 3 and birds, it is claimed, can and do change their sex after birth. For instance, a hen that has laid eggs and hatched them into chickens is said to have later acquired the characteristics and qualities of a rooster and successfully fertilised the eggs of other hens. Such cases have been vouched for by reliable investigators. We know that bees, merely, apparently, by changing the quality of the food supplied to the grub after it is hatched, can convert 'hem at will to queens, drones, or Workers, or ii? farm language to females, males, or an insect of somewhat indefinite gender which, on ocasion, can partially develop into either male or female. Is it possible that what applies to the bees applies equally to the animals? That *ex is dependent on the nourishment the foetus receives during its development ? The study of such problems as this make animal breeding most -sci rating. There is a wide field for thought and experiment, and a rich reward awaits the inquirer who learns how to control Jaws by working in harmony ■with them.