The Living Machine 329 



tion in the cross fertilization experiments just mentioned, 

 there are numerous other evidences of the action of two 

 substances in fertilization. If, for example, the sea urchin 

 egg be treated with the sperm of sharks or roosters, or with 

 the blood or extracts of the organs of some invertebrates, or 

 the blood sera of cattle, sheep, pigs or rabbits, membrane 

 extrusion is induced but development soon ceases, unless the 

 egg be transferred to a strengthened solution of sea water, 

 in which development progresses for a time at least. The 

 initial effect here (membrane extrusion) is the same as that 

 obtained by the use of a fatty acid in artificial partheno- 

 genesis, the second effect (division of the egg) being obtained 

 in the same manner in both cases. There are many other 

 ways in which eggs can be made to develop without fertiliza- 

 tion : brushing the surface of the egg with a fine brush, plung- 

 ing it for a few moments into concentrated sulphuric acid 

 and pricking the egg membrane have all been successfully 

 employed. The egg of even so highly organized an animal as 

 the frog has been made to develop simply by pricking the 

 egg membrane, and the resulting embryo reared to the adult 

 state. 



What more striking evidence could be asked of the physico- 

 chemical nature of life, than the development of a new be- 

 ing by these means ? 



Far distant though we be from a solution of the ''riddle 

 of life" our only present hope of ultimate success is to pro- 

 ceed from the known to the unknown, working on the hy- 

 pothesis that nature is a unity and not a duality, and that 

 the same fundamental laws control organic and inorganic 

 worlds alike. 



