Heterostylous plants may possibly be the means of establishing my view that the law of sexual complements holds good for every kind of living thing. Darwin first, and after him many other investigators have proved that in heterostylous plants fertilisation has the best results, or, indeed, may be possible only when the pollen from a macrostylous flower (a flower with the shortest form of anthers and longest pistil) falls on the stigma of a microstylous blossom (one where the pistil is the shortest possible and the stamens at their greatest length), or vice versâ. In other words, if the best result is to be attained by the cross-fertilisation of a pair of flowers, one flower with a long pistil, and therefore high degree of femaleness, and short stamens must be mated with another possessing a correspondingly short pistil, and so, with the amount of femaleness complementary to the first flower, and with long stamens complementary to the short stamens of the first flower. In the case of flowers where there are three pistil lengths, the best results may be expected when the pollen of one blossom is transmitted to another blossom in which the stigma is the nearest complement of the stigma of the flower from which the pollen came; if another combination is made, either naturally or by artificial fertilisation, then, if a result follows at all, the seedlings are scanty, dwarfed and sometimes infertile, much as when hybrids between species are formed.
It is to be noticed that the authors who have discussed heterostylism are not satisfied with the usual explanation, which is that the insects which visit the flowers carry the pollen at different relative positions on their bodies corresponding to the different lengths of the sexual organs and so produce the wonderful result. Darwin, moreover, admits that bees carry all sorts of pollen on every part of their bodies; so that it has still to be made clear how the female organs dusted with two or three kinds of pollen make their choice of the most suitable. The supposition of a power of choice, however interesting and wonderful it is, does not account for the bad results which follow artificial dusting with the wrong kind of pollen (so-called “illegitimate fertilisation”). The theory that the stigmas can only make use of, or are capable of receiving only “legitimate pollen” has been proved by Darwin to be erroneous, inasmuch as the insects which act as fertilisers certainly sometimes start various cross-breedings.
The hypothesis that the reason for this selective retention on the part of individuals is a special quality, deep-seated in the flowers themselves, seems more probable. We have probably here to do with the presence, just as in human beings, of a maximum degree of sexual attraction between individuals, one of which possesses just as much femaleness as the other possesses maleness, and this is merely another mode of stating my sexual law. The probability of this interpretation is increased by the fact that in the short-styled, long-anthered, more male flowers, the pollen grains are larger and the papillæ on the stigmas are smaller than the corresponding parts of the long-styled, short-anthered, more female flowers. Here we have certainly to do with different degrees of maleness and femaleness. These circumstances supply a strong corroboration of my law of sexual affinity, that in the vegetable kingdom as well as in the animal kingdom (I shall return later to this point) fertilisation has the best results when it occurs between parents with maximum sexual affinity.[3]
[3] For special purposes the breeder, whose object frequently is to modify natural tendencies, will often disregard this law.
Consideration of sexual aversion affords the readiest proof that the law holds good throughout the animal kingdom. I should like to suggest here that it would be extremely interesting to make observations as to whether the larger, heavier and less active egg-cells exert a special attraction on the smaller and more active spermatozoa, whilst those egg-cells with less food-yolk attract more strongly the larger and less active spermatozoa. It may be the case, as L. Weill has already suggested in a speculation as to the factors that determine sex, that there is a correlation between the rates of motion or kinetic energies of conjugating sexual cells. It has not yet been determined, although indeed it would be difficult to determine, if the sexual cells, apart from the streams and eddies of their fluid medium, approach each other with equal velocities or sometimes display special activity. There is a wide field for investigation here.
As I have repeatedly remarked, my law is not the only law of sexual affinity, otherwise, no doubt, it would have been discovered long ago. Just because so many other actors are bound up with it,[4] because another, perhaps many other laws sometimes overshadow it, cases of undisturbed action of sexual affinity are rare. As the necessary investigations have not yet been finished, I will not speak at length of such laws, but rather by way of illustration I shall refer to a few factors which as yet cannot be demonstrated mathematically.
[4] In speaking of the sexual taste in men and women, one thinks at once of the usual but not invariable preference individuals show for a particular colour of hair. It would certainly seem as if the reason for so strongly marked a preference must lie deep in human nature.
I shall begin with some phenomena which are pretty generally recognised. Men when quite young, say under twenty, are attracted by much older women (say those of thirty-five and so on), whilst men of thirty-five are attracted by women much younger than themselves. So also, on the other hand, quite young girls (sweet seventeen) generally prefer much older men, but, later in life, may marry striplings. The whole subject deserves close attention and is both popular and easily noticed.
In spite of the necessary limitation of this work to the consideration of a single law, it will make for exactness if I try to state the formula in a more definite fashion, without the deceptive element of simplicity. Even without being able to state in definite quantities the other factors and the co-operating laws, we may reach a satisfactory exactness by the use of a variable factor.
The first formula was only an abstract general statement of what is common to all cases of maximum sexual attraction so far as the sexual relation is governed by the law. I must now try to find an expression for the strength of the sexual affinity in any conceivable case, an expression which on account of its general form, can be used to describe the relationship between any two living beings, even if these belong to different species or to the same sex.
If
χ ( α M γ ( β W
( α´W and ( β´M(where α, α´, β, and β´ are each greater than 0 and less than unity) define the sexual constitutions of any two living beings between which there is an attraction, then the strength of the attraction may be expressed thus:
A = Kα — β f t
where f t is an empirical or analytical function of the period during which it is possible for the individuals to act upon one another, what may be called the “reaction-time”; whilst K is the variable factor in which we place all the known and unknown laws of sexual affinity, and which also varies with the degree of specific, racial and family relationship, and with the health and absence of deformity in the two individuals, and which, finally, will become smaller as the actual spacial distance between the two is greater, and which can be determined in any individual case.
When in this formula α = β A must be infinity; this is the extreme case; it is sexual attraction as an elemental force, as it has been described with a weird mastercraft by Lynkeus in the novel “Im Postwagen.” Such sexual attraction is as much a natural law as the downward growth of a rootlet towards the earth, or the migration of bacteria to the oxygen at the edge of a microscopic cover-glass. But it takes some time to grow accustomed to such a view. I shall refer to this point again.
If α — β has its maximum value,
