These several examples till recently had been severe stumbling-blocks to the theory that sex is dependent on a dimorphism of spermatozoa. Some animals do possess two kinds of eggs, of which one (the bigger) develops into females and the opposite sort (the smaller) into males; there are various situations of selective fertilization; and lots of animals do produce two sorts of spermatozoa. These investigators are inclined to consider that there are two sorts of eggs as there are two kinds of spermatozoa, and that sex is the result of an interplay or battle of the sex determinants of those parts and the dominance of one or the opposite sex. The apparent and necessary assumptions are that there aren’t any individuals pure in sex; all are hybrids; and the sex that the organism attains is the results of a battle between the mingled male and feminine tendencies and the dominance, now of one tendency, now of the opposite.
Now at fertilization when an egg of 18 chromosomes unites with a spermatozoan of 18 chromosomes an organism whose cells comprise 36 chromosomes results, and it is a feminine; when the opposite combination occurs, 18 chromosomes from egg and 17 chromosomes from sperm, an organism outcomes that has solely 35 chromosomes, and this can be a male. If the egg is feminine in tendency, in order that there ought to appear 50 per cent, males, maleness should dominate over femaleness. In applying Mendelian principles to sex, maleness and femaleness are thought to be unit characters and in the course of the maturation of the germ-cells the carriers (chromosomal parts) of the male and feminine qualities are believed to be segregated in different cells, both ova and spermatozoa, in order that one half of the ova include the male-figuring out issue and the other half the female; and likewise the spermatozoa. Aplopus mayeri (named after Dr. A. G. Mayer, director of the Biological Laboratory of the Carnegie Institution of Washington at Dry Tortugas, Florida) produces two kinds of spermatozoa differing within the number of chromosomes (rod-like our bodies alleged to be the vehicles of the hereditary qualities) that the 2 courses possess.
A certain worm (Dinophilus apatris) carefully studied by Korschelt, is thought to provide two kinds of eggs, giant and small, the former growing into females, the latter into males. But in the case of Hydatina senta, a rotifer or “wheel animalcule,” where giant and small eggs are additionally laid, the former without fertilization turn into females and the latter into males. Also when white mice (albinos) are crossed with gray mice (or pigmented mice) the first generation are all gray, when the latter are bred amongst themselves the second technology consists of albinos and grey individuals in the proportion of 1 pure gray: 2 gray hybrids: 1 pure white. Mendelism is the term employed to designate a set of phenomena that appear when animals or plants with sharply contrasting characters (white flower petals and coloured petals; grey fur and white fur; quick stature and lengthy stature; sagacity and stupidity; and so on.) are crossed.
According to those biologists all animals are sex-hybrids; either sex is potentially current initially, but by reason of the dominance of 1 or the other sex-determinant the actual sex turns into patent and makes the animal definitively male or female. However, each sorts of females, the massive-egglaying variety and the small-egg-laying kind, got here initially from fertilized eggs, and it may be that a distinction in metabolic activity of the several females stored the eggs of the one small and allowed these of another to develop massive and so gave the victory to the female determinant within the effectively-nourished egg. If the accessory chromosome is a sex-determinant, then when an egg is fertilized by a sperm missing this aspect, the egg itself should carry the factor that determines that the sex of the resulting organism of 35 chromosomes shall be a male. Suppose femaleness dominated, then there can be 75 females in each 100 of population or of any explicit species. The nicely-nourished females produce female eggs, the poorly nourished produce male eggs.