THE SYSTEM 71 



what their origin ; it looks as if this were due to 

 a chemical influence, exercised by the optic cup 

 or by the liquid it contains. 



" Lewis has shown that when the optic cup is 

 transplanted into any other place under the 

 epithelium of a larva of a frog the epithelium will 

 always grow into the cup where the latter comes 

 in contact with the epithelium ; and that the 

 ingrowing part will always become transparent." 

 A most remarkable and interesting experiment ; 

 it has this very important limitation that it is 

 always epithelium with which it has to do, whereas 

 in Wolff's experiment the regeneration takes 

 place from mesoblastic tissue. The cause of the 

 transparency may be a chemical reaction it 

 depends a good deal upon our definition of that 

 phrase. Is protoplasm a chemical compound ? 

 Some have considered it so, and spoken of its 

 marvellously complicated molecule. Of course 

 it is made up of carbon, hydrogen, and other 

 substances within the domain of chemistry. But 

 is it, therefore, merely a chemical compound ? 

 The reply involves the whole riddle of Vitalism. 

 The author would say that it, as well as all the 

 living things to which it belongs, is purely and 

 solely a chemical compound ; and he must take 

 the consequences of his belief. One of these 

 consequences, from which doubtless he would not 

 shrink, would be that a super-chemist (so to 

 speak) could write him and his experiments and 

 his book down in a series of chemical formulae 

 a consequence which takes a good deal of believing. 

 But it also involves him in a belief in the rigidity 



