650 . Advances in Knoivledge of Silicon. [May 28, 



show some portions on the screen which have been rendered nearly 

 transparent by soaking in benzene, and under tliese conditions exhibit 

 traces of structure. 



Next as to the Animal kingdom. The most satisfactory evidence 

 that we can at present offer as to the organ-building capacity of 

 silicon comes, curiously enough, from some of the simpler organisms 

 of the Animal kingdom, but the only group the short remaining time 

 at my disposal permits me to notice is that of the Sponges. 



You know that these curious forms of undoubted animal life live 

 in sea-water and are usually anchored to rocks. The sea contains a 

 very minute proportion of silica in solution, and the sponge has the 

 power of appropriating very considerable quantities in the course of 

 its life, and as a part of its normal food supply. What does it do with 

 this silica ? It appears to use it in cell production, and from the cell 

 evolves the beautiful and minute siliceous spicules which are so 

 abundant throughout the structure of many of the sponges. 



I have here some photographs of these spicules which I have had 

 taken, and shall throw them on the screen. Two of the best of them 

 have been made from microscopic specimens kindly lent to me by 

 Professor Dendy, of King's College, London, who has made a special 

 study of these spicules and of their modes of growth. One of these 

 slides is reproduced in the engraving. (See Fig. 1 on Plate.) 



These structures do not represent mere incrustations, but rather 

 definite growths from the cell protoplasm and are themselves in the 

 nature of cells of characteristic forms. Professor Dendy informs me 

 that these spicules in certain cases become surrounded by a horny 

 substance and seem to die, as if by cutting off the supply of energy 

 as well as growing material. 



In some of the larger sponges, as in the beautiful Euplectella 

 aspergillum or "Venus' Flower Basket," represented in Fig. 2, the 

 siliceous material constitutes the greater part of the sponge, as the 

 soft portion resembles a somewhat gelatinous coating from which 

 the exquisite siliceous structure is developed. 



To sum up, then, I have shown that silicon can easily take the 

 place of carbon in many nitrogen compounds, as well as in others 

 not including nitrogen. It therefore seems to me that we hazard no 

 very violent hypothesis in supposing that the silicon w^hich enters the 

 sponge in its food, probably as an alkaline silicate, is in the mar- 

 vellous animal laboratory made to take the place of a portion of the 

 carbon of the protoplasm from which the spicules are ultimately 

 developed. 



The hypothesis is at any rate suggestive, and I hope enough has 

 been said to commend it to your consideration, for there seems to be 

 no doubt that silicon is capable of playing a larger part as an 

 " Organic Element," than we hitherto had reason to suppose. 



[J. E. R.] 



