166 PROCEEDINGS OP THE SOCIETY, 



had made a collection. His series were all excavations made by fungi 

 in calcareous particles; the one before them differed entirely from 

 these. 



Mr. H. Epps exhibited a Culpeper Microscope with wooden base. 



Mr. Mayall said this Microscope was an interesting model, but it 

 was not a very uncommon form. By removing the body-tube they had 

 what was known as the old Wilson form of Microscope, which afterwards 

 became so very popular in connection with the heliostat. This was the 

 same form as several examples in the cabinet of the Society. The 

 maker was Edmund Culpeper, a very careful vrorkman, accustomed to 

 ornament his apparatus with engraved patterns. The general style and 

 finish of the instrument were evidently due to his training as a mathe- 

 matical instrument-maker. 



Mr. T. F. Smith said that about three months ago he brought before 

 the notice of the Society his ideas of what he conceived to be the 

 structure of Pleurosigma formosum ; since that time he had made some 

 further researches upon this diatom and also upon P. angulatum. He 

 then stated that he thought P. formosum might, on closer investigation, 

 prove to consist of more than three layers of structure, but he had come 

 to the conclusion that there were not more than three. By means of 

 drawings on the board, Mr. Smith further explained his views, and 

 illustrated the subject by the exhibition of numerous photomicrographs 

 as well as by specimens under the Microscope of P. angulatum, showing 

 a fine grating hitherto undescribed. 



Mr. E. M. Nelson said, though he could add nothing to what Mr. 

 Smith had told them, he thought it was most difficult work to carry out, 

 indeed the difficulty might be understood from the fact that although 

 this diatom had been of all others the most persistently examined, yet 

 the structure described by Mr. Smith had hitherto escaped notice. 



The President said no doubt it would be extremely desirable to get 

 at what was the real structure of the diatom valve, but he often thought 

 that, considering the conditions, it might be impossible after all to get 

 at it. He did not profess to be competent to judge on a matter of this 

 kind, but he often met with illustrations in the Eotifera which led him 

 towards that conclusion. He was once greatly struck by the apparent 

 alteration in]the striations in the muscle of one of the Eotifera, which 

 he had been very carefully observing and measuring. In watching 

 Triarthra he distinctly saw the size of the strite alter in fineness whilst 

 under observation. Owing to there being parallel layers through which 

 he was looking, the movement of the muscle caused an alteration in their 

 relative positions, and so entirely changed the appearance, as to render 

 all his previous measurements useless. 



Mr. Crisp exhibited the Bausch and Lomb Optical Co.'s spirit-lamp, 

 the reservoir of which was facetted instead of globular, so that it might 

 be used in various positions — vertical, inclined, or horizontal. Also 

 Mawson and Swan's photomicrographic arrangement for fixing on the 

 front of an ordinary camera. Also the fitting for the binocular prism 

 of Messrs. Bausch and Lomb, by which the prism instead of sliding was 

 rotated out of the field. Also Falk's rotating object disc for bringing a 

 number of objects in succession under the objective. 



