IN THE MUD OF THE LEVANT. 23 



aniraality.* Mr. Hogg, in his investigation on 

 the action of light as affecting the colour of the 

 river sponge, Spongilla flumatilis,^ has advanced 

 good arguments in favour of its being a plant, a 

 conclusion in which most naturalists are now 

 ao-reed. Dr. Bailey has pointed out the existence 

 of siliceous spicula in unquestionably fresh-water 

 deposits in the state of Maine, U. S., so analogous 

 to those of some marine sponges as to be almost 

 identical ;| yet they are doubtless those of a 

 fresh-water species. This is supported by Struve's 

 analysis of the Spongilla, in which he found, 

 that the ashes left after combustion contained 

 94.66 per cent of silica.§ These facts indicate a 

 close affinity between the marine and fresh-water 

 forms, and, consequently, increase the probability 

 that the former are more closely allied to the vege- 

 table than to the animal world. On the other hand, 

 the existence of analogous siliceous spiculain Cliona 

 and Anthopora and calcareous ones in the tissues 



* Mr. Bowerbank on the Organic Tissues in the Bony 

 Structure of the Corallidee. Phil. Trans. Royal Society. 

 1842. Parti, p. 219. 



t Paper read to the Royal Society, June 21, 1838. 



X Silliman's Journal. Vol. xlvi. p. 307. 



§ Records of General Science, 1836. Vol. iii. p. 157. 



