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Updated: June 26, 2025
If there are an odd number of chromosomes, 2N-1, in all the gametocytes of the male, as stated in most accounts of the subject, then if one chromosome fails to divide in the homotypic division, we shall have 2N-2 in one spermatocyte and 2N-1 in the other.
What meaning are we to attach to the words 'male ovum' or even 'male producing ovum'? It is a fundamental principle of Mendelism that the soma does not influence the gametocytes or gametes; we have therefore only to consider the sex of the gametes themselves, derived from a zygote which is formed by the union of two sexes.
The theory proposed by me in 1908 was that we have within the gonads numerous gametocytes whose chromosomes contain factors corresponding to the different parts of the soma, and that factors or determinants might be stimulated by products circulating in the blood and derived from the parts of the soma corresponding to them.
How comes it then that the female quality entirely disappears? Whether the gametocytes are distinguishable at an early stage in the segmentation of the ovum, or only at a later stage of development, we know that the gametes ultimately formed have descended by a series of cell-divisions from the fertilised ovum or zygote cell from which development commenced.
Whether the mixture of the chromosomes occurs in every resting stage of the nucleus in the successive generations of the gametocytes, or whether it occurs only in the synapsis stage preceding reduction division, it is not surprising that the colloid substance of the chromosomes should form a more or less complete intermixture, and that the two original chromosomes should not be again separated in the pure condition in which they came into contact.
Instead of saying that the zygote composed of ovum and spermatozoon is incapable of giving rise in the male to ova, or in the female to sperms, we should hold that the gametocytes ultimately give rise to ova or to sperms according to the metabolic processes set up and maintained in them through their successive cell-divisions under the influence of the double or single X chromosome.
If there were no special relation, hypertrophy of bone on one part of the body such as the head, would merely stimulate the factor for the whole skeleton in the gametocytes, and the result would merely be an increased development of the whole skeleton.
There still remains the difficulty of explaining why the male gametocytes after reduction develop into similar sperms, with their heads and long flagella, although half of them possess one X chromosome each and the other half none.
The sex-chromosome in the male gametocytes is single and fails to divide with the others, but passes undivided to one pole. But it is difficult to understand what is meant by 'fails to divide. In one of the reduction divisions all the chromosomes divide as in ordinary or homotypic nucleus division, but in the other the chromosomes simply separate into two equal groups without division.
The question at once arises whether the soma itself is sexual, that is to say, whether on the assumption that the sex of the zygote is already determined before it begins to develop, the somatic cells as well as the gametocytes are individually and collectively either male or female.
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