PROCEEDINGS OF SOCIETIES. 24!) 



his method of illimiination by extremely oblique light, and exhibited 

 some specimens of Triceratium, in which the small disks at the angles 

 of the hexagons, usually seen as beads, were shown to be really 

 depressions or " craters." 



Mr. M. Hawkins Johnson, F.G.S., read a paper " On Silicified 

 Structures in Pyritized Wood." A description was given of the 

 fossil wood-stems found, at low water, on the north coast of the Isle 

 of Sheppey, having been washed up out of the London clay. These 

 consist principally of iron pyrites, and are used in the manufacture 

 of sulphuric acid. On dissolving the iron pyrites by nitric acid, 

 acting upon a smooth section, the woody structure, which appears to 

 have become silicified, is left in relief. The conclusions drawn were 

 that the silicification was due to the rej)lacement of the carbonaceous 

 walls of the wood-cells by silicon, and that the pyritous infiltration 

 subsequently filled the pores of the structure. 



Mr. Charles Stewart, M.R.C.S., &c., at the invitation of the 

 President, gave a very interesting description of the hard parts of 

 Echinoderms, which he considered to rank amongst the most beautiful 

 objects claiming the attention of the microscopist. He enumerated 

 the various groups into which the class was divided, and described 

 their general characteristics. He then gave a detailed account of the 

 Echini, figuring the typical forms, and minutely describing their 

 anatomy, and the structure and arrangements of the spines, ambulacral 

 disks, and pedicellarise. Numerous specimens of the hard structures 

 of Echinoderms were exhibited under several microscopes in illustra- 

 tion of the subject. 



Adelaide Microscopical Club, South Australia.* 



The monthly meeting was held on August 20, 1875, Mr. Young in 

 the chair. Mr. Babbage exhibited objects for polariscope. Dr. Whittell 

 exhibited a thin section of a cancer of breast removed four weeks ago. 

 The section had been cut so as to include a portion of the adipose 

 tissue, and the interest of the preparation lay in the fact that the can- 

 cerous cells were just beginning to invade the fatty tissue. It was 

 determined to hold a conversazione in September or early in October. 

 Several members promised to assist, and it was recommended that, as 

 far as possible, the members exhibit objects prepared by themselves, 

 and of local interest. The Chairman then gave a short address on 

 Pond-life, which he illustrated by objects brought from ponds near 

 his residence. He said these would have been more numerous, but 

 he found the season was not so far advanced as in former years, and 

 many confervoid growths had not yet made their appearance. Among 

 the objects of interest were several specimens of the Desmidiacese, 

 a beautiful specimen of Volvox resembling the Volvox globator of 

 England, but differing from it in a few minor details. A specimen 

 of Nitella in which the circulation could be distinctly seen was also 

 exhibited. This attracted the attention of members because many 

 of them had failed to find in South Australia a plant in which the 



* Report supplied by Dr. Whittell. 



