FERTILISATION OF THE EGG-CELL 215 



the appearance of a mulberry, each granule of the berry 

 being a cell provided with its own nucleus derived from 

 the original nucleus formed by the fusion of the nuclei of 

 the paternal and maternal cells. In the course of a day 

 or two the division has proceeded so far that the resulting 

 " cells " are so small as to be invisible with a hand-glass, 

 and require one to use a high magnifying power in order 

 to distinguish them. And there are hundreds of them ; 

 the whole mass of the " egg " within, as well as on the 

 surface, has divided into separate cells. They go on 

 multiplying, take up water, and nourish themselves on the 

 granular nutritive matter present from the first in the egg- 

 cell. The little mass elongates, increases in size, and 

 gradually assumes the form of a young tadpole. 



We see, then, that the process of fertilisation consists in 

 two things, the latter of which necessitates the former, viz. in 

 the breaking or penetration of the surface of the egg-cell by 

 the active sperm filament, and second, in the fusion of the 

 substance of the sperm-filament with that of the egg in 

 such a way that there is a distinct and intimate fusion of 

 the nucleus of the sperm filament with the nucleus of the 

 egg-cell. The recent discovery of M. Bataillon is this, viz. 

 that you can make the frog's egg develop in a perfectly 

 regular way and become a tadpole and then a young frog 

 without the admission to it of a sperm-filament or of any 

 substance derived from the male frog. All you have to 

 do — and the operation, though it sounds easy and simple, 

 is an exceedingly delicate and difficult one — is to prick 

 with a fine needle the surface of the little black egg-sphere 

 (not merely of the jelly surrounding it) when it is shed by 

 the female frog into perfectly pure water free from sperms 

 or anything of the sort. The slight artificial puncture 

 acts as does the natural puncture by the swimniing sperm- 

 filament, and is sufficient ! The egg proceeds to develop 

 quite regularly. There is no fusion of the nucleus of the 



