VI.] THEIR SIGNIFICANCE IN HEREDITY. 389 



all, cannot be restricted to the germ-cells of animals. There 

 must be a corresponding process in plants, for sexual repro- 

 duction is essentially the same in both kingdoms ; and if 

 fertilization must be preceded by the expulsion of half the 

 number of ancestral germ-plasms from the eggs of animals, 

 the same necessity must hold in the case of plants. 



But whether the process always takes place in the form of 

 polar bodies, and not perhaps principally, or at any rate fre- 

 quently, in the form of equal cell-division, is another question. 

 It is true that polar bodies occur in numerous plants, as we 

 chiefly know from Strasburger's researches ^ Strasburger 

 shows that cells are separated by division from the germ- 

 cells, and perish. But it seems to me doubtful whether we 

 must always regard their formation as the removal of half the 

 number of ancestral germ-plasms rather than the histogenetic 

 nucleoplasm of the germ-cell. It appears to me that histo- 

 genetic nucleoplasm must be present in the highly differentiated 

 vegetable germ-cells, especially in the male cells, and also that 

 it must be removed during the maturation of the cell, if my 

 idea of the histogenetic nucleoplasm be accepted. It is very 

 possible, as I have already mentioned, that there may be quite 

 indifferent germ-cells, viz. cells which are entirely without 

 specific histological structure, and in such cases histogenetic 

 nucleoplasm would be absent ; and during the maturation of 

 such germ-cells no polar body would be formed for its removal. 

 This view accords with the fact that polar bodies are absent in 

 many plants. Furthermore, I am far from maintaining that in 

 the cases where polar bodies occur, they must have the above- 

 mentioned significance. I only wish to point out that the 

 reduction assumed to be necessary for the nucleus of the 

 vegetable germ-cells is not necessarily to be sought for at the 

 close of their maturation, but perhaps even more frequently in 

 an equal division of the germ-cells during some period of their 

 development. 



It also seems to me to be not impossible that a number of 

 these vegetative * polar bodies ' may have an entirely different 

 significance, viz, to perform some special function accessory to 

 fertilization, as in the so-called 'ventral canal-cells' of the 

 higher cryptogams and conifers. As we know that even the 



^ I. c, p. 92. 



