240 THE EVOLUTION OF LIFE 
_extremely interesting and suggestive, since silicon is 
certainly the element which most closely resembles 
carbon, and which might therefore best replace it in 
compounds otherwise similar to those which con- 
stitute the basis of living matter. A silicon alcohol 
and ether has in fact been produced by Professor 
Wohler,! in which the carbon of the ordinary com- 
pounds is replaced by silicon. It is therefore 
deemed quite possible that silicon may take the 
place of carbon in certain forms of living matter. No 
absolute proof of this, however, can at present be ad- 
vanced. What follows must be taken merely as an 
indication of the possibility of such an occurrence.” 
Reference was then made to an observation of my 
own, in which a mass of mould was found growing 
luxuriantly on the surface of some silicate of soda 
solution, contained in a corked bottle which had 
been unopened for about six months. Attention 
was also called to the previous observations of Messrs 
Roberts (afterwards Sir Wm. Chandler Roberts) and 
Slack on solutions of hydrate of silica, as recorded 
in the Quarterly Journal of Microscopical Scrence for 
1868 (pp. 105-108), in which they say: “All the 
specimens of silica solution supplied by Mr Barff to 
Mr Slack, whether kept in bottles nearly full and 
corked, in bottles containing much air, or in open 
vessels, exhibited the mildew threads in the course 
of a week or ten days.” After recording some 
further observations and experiments, they say, in 
conclusion, ‘‘ The preceding experiments show the, 
facility with which moulds will grow in a solution of 
i This is not quite correct. But see p. 279, Note:t, 

