He arrives at the conclusion that the sex of the higher animals and plants is determined in the egg. He arrives at this conclusion within the face of an overwhelming body of proof to the opposite, for in the good majority of kinds all the spermatozoa which are formed develop in the same means and are, as far as we are able to see, capable of fertilizing the eggs. Prom this he attracts the fairly sweeping conclusion that all through the animal kingdom one among the two types of spermatozoa has grow to be suppressed. On this animal there are hair-like spermatozoa that resemble the strange forms of spermatozoa, and in addition worm-like types that are as quite a few as the other variety. Beard calls consideration to the fact that in almost all the circumstances in which two sorts of spermatozoa have been described there may be evidence of the degeneration of certainly one of the two sorts. Within the lengthy checklist of instances given by Beard wherein two forms of spermatozoa have been described, there are several circumstances wherein the 2 distinct kinds appear to be all the time current and characteristic, as in the instances cited above; however he has also included some other cases through which large spermatozoa occur, and a few of these at the least have been shown to be the result of a failure of the spermatocytes to divide.
The gray colour of the grey mouse is said to be dominant and the white shade (inherited from the other mother or father) doesn’t appear, however is speculated to be present in a kind of latent situation. As utilized to our illustration of the mice it would be as follows: When the egg of the white mouse is fertilized by the spermatozoon of the gray mouse the fertilized egg and all of the cells into which it divides comprise chromatin material within the nucleus half from the white and half from the gray mum or dad. If now these primary hybrid mice are interbred a few of their younger shall be white and the remaining grey within the proportion of 1 to 3. A number of the grey mice will even breed true, however the remainder that are grey hybrids will, if interbred, give rise to some white and a few gray in the proportion once more of one to a few.
Suppose now that these hybrids breed collectively, the white and the black spermatozoa will meet the white and the black eggs, and since it’s a question of probability alone how they’ll come together, all attainable mixtures might be made. Finally every of those cells produces 4 spermatozoa. He makes an attempt to deliver the problem of the differentiation of the sexes into connection with the latest work relating to the origin of the reproductive cells or gametes. The proof on which Castle rests his assumption that there are two kinds of spermatozoa, in addition to two sorts of eggs, is contained in the next assertion: “That sex is borne by the egg is shown clearly by the case of parthenogenetic animals, which without the intervention of a male produce younger of each sexes. That the spermatozoon additionally bears sex is manifest within the case of animals just like the honey bee, for the egg of the bee, if unfertilized, invariably develops right into a male, but if fertilized right into a female.” The finality of the conclusions drawn from these details is on no account above question. The cells of this major hybrid that have gone into the reproductive organs (in the female into the ovary and within the male into the testis) are alleged to be at first like all the other cells of the body, and comprise each white and dark components.
5. One set of these fourfold teams of spermatozoa Beard supposes to have change into functionless, within the sense that even when it develops the spermatozoa have misplaced the power to fertilize the eggs. Whenever we discover long series of parthenogenetic females, as in the aphids, developing from and in addition producing parthenogenetic eggs, Beard supposes that solely female eggs have been produced within the ovary, and that the male eggs, which have appeared in a single not less than of the primary generations of the germ-cells ‘must be either delayed in their ripening or suppressed.’ Here we meet with a paradox that is so patent and touches such a elementary level of Beard’s principle that it is more than stunning that he has stated nothing about it. Furthermore, Castle supposes that the separation of the male from the feminine qualities of each egg takes place at the time when the second polar physique is extruded, and, in consequence, the egg and one of the polar bodies will probably be female and the opposite two polar bodies male, or if the egg remains female, one polar body might be female and the other two male. Though I’m talking about first time sex right here, my personal definition of that is fairly broad.