374 ON THE NUMBER OF POLAR BODIES AND 



a division, all means such as cells used as food, or the passage of 

 food from follicular cells into the ovum, etc. are employed in 

 order to bring- the egg-cell to the greatest attainable size. Fur- 

 thermore, the ' reducing division ' of the nucleus cannot take place 

 before the egg has attained its full size, because the ovogenetic 

 nucleoplasm still controls the egg-cell, and must be removed before 

 the germ-plasm can regulate its development. By arguments such 

 as these I should attempt to render the whole subject intelligible. 



But the case is entirely different with the sperm-cells, which 

 are generally minute: here it is quite conceivable that a 're- 

 ducing division ' of the nuclei may take place by an equal division 

 of the sperm-cells, occurring towards the end of the period of their 

 formation ; that is to say, in such a way that both products of 

 division remain sperm-cells, and neither of them perishes like the 

 polar bodies. But the other possibility also demands consideration, 

 viz. that the reducing division may occur at an earlier stage in the 

 development of sperm-cells. At all events, the arguments adduced 

 above, which proved that the consequence would be a want of vari- 

 ability in the egg-cells, would not apply to an equal extent in the 

 case of the male germ-cells. Among the egg-cells it may be very 

 important that each one should have its special individual cha- 

 racter, produced by a somewhat different composition of its germ- 

 plasm, inasmuch as a considerable proportion of the eggs frequently 

 developes, although this is never the case with all of them. But 

 the production of sperm-cells is in most animals so enormous that 

 only a very small percentage can be used for fertilization. If, 

 therefore, e. g. ten or a hundred spermatozoa contained germ-plasm 

 with exactly the same composition, so that, as far as the paternal 

 influence is concerned, ten or a hundred identical individuals would 

 result if they were all used in fertilization, such an arrangement 

 would be practically harmless, for only one spermatozoon out of an 

 immense number would be employed for this purpose. From this 

 point of view we might expect that the ' reducing division ' of the 

 sperm-nucleus would not take place at the end of the development 

 of the sperm-cell, but at some earlier period. There is no necessary 

 reason for the assumption that this division must take place at the 

 end of development, and without some cause natural selection can- 

 not operate. It is, of course, conceivable that the causes of other 

 events may also involve the occurrence of this division at the end 



