140 THE EIDDLE OF THE UNIVERSE. 



sensitive action of the protoplasm, allied to smell 

 or taste, which we call " erotic chemicotropism "; it 

 may also be correctly (both in the chemical and the 

 romantic sense) termed " cellular affinity "or " sexual 

 cell-love." A number of the ciliated cells in the 

 sperm swim rapidly towards the stationary egg-cell 

 and seek to penetrate into it. As Hertwig showed 

 in 1875, as a rule only one of the suitors is fortunate 

 enough to reach the desired goal. As soon as this 

 favoured spermatozoon has pierced into the body of 

 the ovum with its head (the nucleus of the cell), a 

 thin mucous layer is detached from the ovum which 

 prevents the further entrance of spermatozoa. The 

 formation of this protective membrane was only 

 prevented when Hertwig kept the ovum stiff with 

 cold by lowering the temperature, or benumbed it 

 with narcotics (chloroform, morphia, nicotine, etc.) ; 

 then there was "super-impregnation" or " poly- 

 spermy " — a number of sperm- threads pierced into 

 the body of the unconscious ovum. This remarkable 

 fact proved that there is a low degree of " cellular 

 instinct " (or, at least, of specific, lively sensation) 

 in the sexual cells just as effectively as do the 

 important phenomena that immediately follow in 

 their interior. Both nuclei — that of the ovum and 

 that of the spermatozoon — attract each other, approach, 

 and, on contact, completely fuse together. Thus 

 from the impregnated ovum arises the important new 

 cell which we call the " stem-cell " (cytula), from the 

 repeated segmentation of which the whole polycellular 

 organism is evolved. 



The psychological information which is afforded by 

 these remarkable facts of impregnation, which have 

 only been properly observed during the last twenty- 



