170 



THE EVOLUTION OF SEX. 



" In both cases the beginning of development depends upon the presence 

 of a definite, and indeed similar mass of germ-plasma. In the ovum which 

 requires fertilization, this is afforded by the importation of the sperm-nucleus, 

 and development follows on, the heels of fertilization. The parthenogenetic 

 ovum already contains the necessary mass of germ-plasma, and this becomes 

 active as soon as the single polar body has freed the ovum from the ovogenetic 

 nuclear-plasma." 



Now if it be true that a constant difference between an egg which can 

 develop of itself and one which can not, is that the former extrudes one tiny 

 cell, and the latter, so far as yet observed, two, Weismann must be right in 

 emphasizing that part at least of the secret of parthenogenesis lies here. Partly 

 hidden still, however, if one dare ask what there is about the parthenogenetic 

 ovum which limits its primitive budding to once instead of twice. Not 

 altogether so subversive of Minot's theory either, as Weismann would make 

 out. Minot, as we saw, accepts the facts, but ingeniously supposes that the 

 polar element retained in parthenogenetic ova is a male element. It is neces- 

 sary, however, to examine Weismann's theory more closely, not only in its 

 direct relation to the problem of parthenogenesis, but because of its postulates, 

 which run so directly counter to our reading of the phenomena of sex. 



1. Weismann's theory obviously differs very emphatically from those pre- 

 viously suggested. The first polar body is no skimming of antagonistic male 

 material ; the very reverse, it is an extrusion of ovogenetic nuclear material 

 which had to do with the upbuilding of the ovum, an emphatically female 

 function. Nor is the second polar extrusion in any way an expulsion of male 

 elements ; it is a giving away of some of the precious germ-plasma, the bearer 

 of hereditary characteristics. Furthermore, even the sperm nucleus is in no 

 peculiar sense male material ; it might as well be another ovum-nucleus. It 

 has only a quantitative value, to restore to the nucleus of the ovum an amount 

 of germ-plasma equivalent to that which has been so recklessly squandered. 



2. But Weismann's theory, based on the observation of facts, is in itself full 

 of hypotheses. This distinction between ovogenetic and germ-plasma within 

 the germinal vesicle is an unverifiable myth. That the first polar body is an 

 extrusion of one kind of nuclear substance, and the second something quite 

 different, is another unproved hypothesis. Were the extrusions markedly 

 different, one might believe it, but they are the same. When a large cell 

 divides very unequally, as in polar-body formation, there is some warrant for 

 supposing that the little bud is different .from the large cells ; but that two 

 successive divisions, entirely similar in character, are conspicuously different, 

 requires faith. It is allowed by all that each polar division lessens the mass 

 (not the number) of the chromatin elements in the nucleus by a half, but so far 

 as nucleus is concerned there is nothing whatever to show that the first division 

 is qualitatively different from the second. The first may have more cell- 

 substance extruded along with it, and the second may be rather a nuclear than 

 a cell-division, but as regards "plasma" the two are, so far as the facts go, 

 absolutely alike. The second division also follows on the heels of the first 

 without the intervention of the usual resting-stage. Nor of course is there any 

 proof that a parthenogenetic ovum does not part with half its "germ-plasma " 

 in the first division. The distinction between the two kinds of nuclear plasma 

 is, in plain words, a myth. 



3. Weismann's preoccupation with questions of inheritance has given a bias 

 to his theory, making it morphological rather than physiological. A given 

 quantum of germ-plasma, he says, fits the ovum to develop. The partheno- 



