UNION OF SPERM -CELL AND GERM- CELL. 335 



sperm- cell to the union of an acid with its base. But 

 the deeper our researches penetrate, the more erroneous 

 does such a comparison appear. I cannot pause here 

 to trace the genesis of ovum and spermatozoon, but 

 must content myself with the assertion, wliich the 

 reader can verify by consulting any embryological 

 authority, that in their origin, and in the earlier phases 

 of their development, these two cells are identical. It 

 is only in their subsequent history that they differ.* 

 If one convincino' aro'ument be needed to crown all 

 these indications, we may find it in the now indubitable 

 fact, that animals which normally are developed from 

 fertilised eggs, are also normally developed from eggs 

 unfertilised. It is clear, then, that if the Qgg, previous to 

 fertilisation, has within it the elements and conditions 

 which tuill produce the same animal as would have 

 issued from the fertilised egg, the influence of the 

 sperm-cell on the germ-cell, whatever it may be, cannot 

 be of that elementary indispensable nature which is 

 implied in the comparison of an acid uniting with a 

 base to form a salt. No alkali spontaneously develojDS 

 into a salt ; without the acid the alkali is powerless to 

 assume any of the saline forms. But the germ-cell 

 does develop an embryo without the aid of a sperm- 

 cell ; and this, too, in certain animals which at other 

 times generate sperm-cells. Indispensable the influence 

 of the sperm-ceU is, in the more complex organisms 

 (although the insect is a very complex organism) ; but 



* That is the reason why plants can be developed into male or female 

 according to the will of the experimenter. 



