SEX-DETERMINATION.

[We take this opportunity to inform our readers that we have arranged with Mr. Julian.Huidey, who is at present visiting. Canada

and the United States on the occasion of the British Association's Meeting at Toronto, for the publication of a series of articles by him on various American =subjects. Mr. Husky has suggested the following topics, but he will vary this list. These articles will begin to appear about the 'middle of September

:- (1) " Higher Education in the United States " ;

(2) " Thee Fundamentalists " (3) "The Negro Problem and its Biological Aspect " ; (4) " Prohibition " ; (6) "A Comparison of Canada and America "--; (6) " The Quota " -

;7) "Religion in Zmerica." —ED1 Spectator.] THERE has been a good deal of stir in the newspapers recently over- the elaim....made by the wife of an tha,t the sex of a child can be cleterminedin advance. It is a pity that people do, not take the trouble to look into the.history of the:subject, when they would find.that in :ninety-nine cases out of a hundred the " new " theory of sex-determination has been .advanced (and exploded) a dozen times already ; or to. discover what has actually _been established by science, when they would be able to see what further -theories were possible, what. impossible. This latest -claim asserts that the sex of the offspring is in some xelation with the time of conception. There are .two old midwives' superstitions on this subject. One is that sex is determined by the -time of conception in relation to woman's periodic cycle—in other words, by the -state- of the ovum.. It is usually asserted that fresh and fully-xipe ova give females, over-ripe ones males. The other claims, that, sex is determined not by the state of the ovum, but by the period, the ovum liberated at one period being destined to give a boy, at the next a girl, and..so mu alternately throughout life. Simple arithmetic would therefore give complete sex-control.

The first belief bas been very thoroughly investigated of labe years, and a German worker, Siegel, claimed that he had definitely verified it from his statistics. On analysis, however, it was found that these were quite unreliable, and there is much evidence (e.g., from the practices of certain ,peoples, such as strict Jews) which contradicts it. For lower mammals this.same superstition has also ,existed. In them it is possible to obtain more satisfactory records ; and a great mass of data for cattle has recently been worked up and the belief shown here also to have no foundation.

The second superstition was exploded before the first. In the first place it would, to say the least, be very re- markable if man were wholly different from other mam- mals in his method of sex-determination ; and it is clear that it does not apply in animals -which have many young at a birth. And secondly, the figures which we possess show pretty clearly that it does not happen. At any rate, they show that any possible effect is very small ; there is no question of complete determination by this means.

Apropos of this, it is well to remind ourselves that statistics only acquire cogency as the number of cases mounts up. If I tell you that I tossed a penny yesterday, and that it came down heads every time, you will not be surprised if you discover that " every time " meant two or yet five times ; and even ten times would not be too unlikely for chance ; but if it happened a hundred times you would rightly conclude that " it meant something." Conclusions about sex-determination drawn from a few -families are wholly useless as proof, although they may be valuable as an indication of what line of investigation to pursue further.

* * * * * It would be a thankless task exploding superstitions if there were no positive results to put in their place. But there are. And the lamentable fact is that, although they can be ascertained in any good library, people will not take the trouble to look them up.

There is one fact concerning sex-determination in mammals which has emerged quite clearly from the last quarter-century's work in biology. It is that in man and all other mammals sex is not primarily determined by anything in the ovum or in the female at all, but by the existence of two kinds of reproductive cells in the male. Thanks to much work by microscopists and Mendelians, and especially thanks to Professor Morgan of New York, we now know that the essential organs of heredity are the so-called chromosomes. These are bodies of definite constitution and number which make up the essential part of the central nucleus of each cell. Each adult man or higher animal possesses two complete sett or packs of these chromosomes in each of his cells. Shortly before the reproductive cells are formed, however, there is a sorting out of the two packs in -such a way that each reproductive cell, ovum or sperm, contains .one pack only. -Fertilization, or the starting of a new life, -consists essen- tially in-the union of sperm with ovum, and the mingling of two single packs of chromosomes into a new double pack.

There -is, however, a difference between the chromo- somes of male and female. In all mammals, the male has one less chromosome than the female.* As regards one particular kind of chromosome, therefore (let us call it X), the female has two, the male one—XX as against X0.

When reproductive cells come to be formed, all the ova get one X. But of the sperms, only half can receive an X ; the other half must be without one. It will now be 'clear in what the sex-determining mechanism consists. The X-bearing sperms are female-determining, those without an X male-determining :—X sperm -I- X egg = XX individual = female ; 0 sperm + X egg = X0 = male.

There are two main lines of evidence on this point. One deals with direct observations through the micro- scope : we can see the two X's in the female, the solitary * It would be more accurate to say one less effective chromosome. In many species one chromosome of the male is apparently a degenerate and certainly ineffective chromosome, instead of boil= wholly absent: the principle, however, _remains the same. X in the male. The other concerns a special type of inheritance• known as sex-linked. The two are in com- plete agreement. The matter has recently been clinched ,in another way. The so-called " head " of the sperm consists of little else but the condensed chromosomes. The head of the X-bearing sperms ought therefore to be larger than that of those without an X. Direct measure- ment under the microscope has shown that this is actually so, not only for rats, mice, dogs, horses, cattle and pigs, but for man himself.

* This, then, is the fundamental basis of human sex- determination. The precise method by which the presence of an extra X-chromosome determines female- ness and vice versa is not yet understood. It also seems clear that, exceptionally, other agencies may override the chromosome's authority, converting what ought to have been a female into a male or vice versa, as in some of Dr. Crew's " sex-reversed " fowls ; but it is perfectly certain that such exceptions are extremely rare. It may well prove that particular conditions of the ovum may sometimes help to override the normal machinery : but it will remain certain that this will only bring about a slight alteration in the proportions of boys and girls. Even the much-advertized " compensation of nature "- the excess of male births as a result of war—turns out to be a matter of a paltry 1 per cent. alteration in sex-ratio !

So far as we can see at present, there is only one possi- bility of controlling sex in man or other mammals. That is by separating the large-headed and the small-headed sperms from each other, and proceeding to artificial fertilization. The obtaining of this result is a mere matter of technique ; it should come within fifty years. But whether mankind will choose to employ the method is another matter.

What biology can as yet assert is certainly nothing but the merest foundation ; but it is positive and per- fectly definite. Any theory which runs counter to these positive conclusions must be backed by a great weight of evidence before it can be seriously considered. No one will be happier than the biologists to consider any evi- dence ; but so far no proper statistical data in support of any other theory has been forthcoming. In case Mrs. Erskine is thinking of collecting some, I would like to warn her (experto crede !) that it is a tiresome job, and that the inaccuracy and unscientific habits of mind of the average man in matters outside his business are unbeliev-