370 ON THE NUMBER OF POLAR BODIES AND 



Nevertheless Hensen is the only writer who has hitherto taken 

 into consideration the idea that sexual reproduction causes a 

 regularly occurring ' diminution in the hereditary elements of 

 the egg.' 



III. THE FOREGOING CONSIDERATIONS APPLIED TO THE MALE 



GERM-CELLS. 



If the result of the previous considerations be correct, and if 

 the number of ancestral germ-plasms contained in the nucleus of 

 the egg-cell destined for fertilization must be reduced by one half, 

 there can be no doubt that a similar reduction must also take 

 place, at some time and by some means, in the germ-plasms of the 

 male germ-cells. This must be so if we are correct in maintaining 

 that the young germ-cells of a new individual contain the same 

 nuclear substance, the same germ-plasm, which was contained in the 

 fertilized egg-cell from which the individual has been developed. 

 The young germ-cells of the offspring must contain this substance 

 if my theory of the continuity of the germ-plasm be well founded, 

 for this theory supposes that, during the development of a fer- 

 tilized egg, the whole quantity of germ-plasm does not pass through 

 the various stages of ontogenetic development, but that a small 

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

 cells of the young organism, after having undergone an increase 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 understand 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 expulsion 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 Stras- 

 burger, and if its final ontogenetic stage resulted in the re-appear- 

 ance of the initial condition of the germ-plasm, we should fail to 



