382 ox THE NUMBER OF POLAR BODIES AND [VI. 



part remains unchanged, and at a later period forms the germ- 

 cells of the 3'oiing organism, after having undergone an in- 

 crease in quantity. According to this supposition therefore 

 the germ-plasm of the parents must be found unchanged in 

 the germ-cells of the offspring. If this theory were false, if 

 the germ-plasm of the germ-cells were formed anew by the 

 organism, perhaps from Darwin's 'gemmules' which pour into 

 the germ-cells from all sides, it would be impossible to under- 

 stand why it has not been long ago arranged that each 

 germ-cell should receive only half the number of the ancestral 

 gemmules present in the body of the parent. Hence the ex- 

 pulsion of the second polar body — assuming the validity of 

 my interpretation— is an indirect proof of the soundness of the 

 theory of the continuity of the germ-plasm, when contrasted 

 with the theory of pangenesis. If, furthermore, a kind of 

 cyclical development of the idioplasm took place, as supposed 

 by Strasburger, and if its final ontogenetic stage resulted in 

 the re-appearance of the initial condition of the germ-plasm, 

 we should fail to understand how any of the ancestral germ- 

 plasms could be lost during such a course of development. 



Whichever view, the latter or the theory of the continuity of 

 the germ-plasm, be correct, in either case the male germ-cells 

 of the young animal must contain the same germ-plasm as that 

 which existed in the fertilized maternal c:gg^ that is to say, they 

 must contain all the ancestral germ-plasms of the father and 

 the mother. Here therefore a reduction must occur, for other- 

 wise the number of ancestral germ-plasms would be increased 

 by one half at every fertilization. The egg-cell would furnish 

 i, but the sperm-cell § of the total quantity of germ-plasm 

 present in the germ-cells of the parents. But there is no 

 reason for believing that the reduction of germ-plasm in the 

 sperm-cell must proceed in precisely the same way as in the 

 egg-cell. viz. by the expulsion of a polar body. On the contrary, 

 the processes of spermatogenesis are so remarkably different 

 from those of ovogenesis that we may expect to find that 

 reduction is also brought about in a different manner. 



The egg-cell does not expel the superfluous ancestral germ- 

 plasms until the end of its development, and in a form which 

 induces the destruction of the separated portion. This is 

 certainly remarkable, for germ-plasm is a most important 



