MICROSCOPY. 369 



the mode of production by division of the Desmids. lie ob- 

 served the process in Euglypha alveolata, and found it sim- 

 ilar to the multiplication of Chlamydophrys, as already no- 

 ticed by Cieukowsky. 



Supposed Radiolarians and Diatomacese of the Coal -Measures. 



At the Dublin meeting of the British Association, Pro- 

 fessor W. C. Williamson called attention to the Traquarice 

 of Mr. Carruthers, which were found in the lower coal- 

 measures of Lancashire and Yorkshire, with small spherical 

 objects supposed to be Radiolarians. After thorough exam- 

 ination, Professor Williamson rejects the idea of their Radio- 

 larian character ; while their close organic resemblance to 

 some obviously vegetable conceptacles found in the same 

 coal-measures suggested that the Traquarice are also vegeta- 

 ble structures. 



Count Castracane having published an account of a proc- 

 ess by which he reduced numerous specimens of coals to very 

 minute quantities of coal-ash, in which he found numerous 

 marine and fresh -water Diatomacece, Professor Roscoe de- 

 tailed one of his ablest assistants, in his laboratory at Owens 

 College, to prepare analyses of a number of coals according 

 to Count Castracane's method. The residual ashes were 

 mounted microscopically and examined by Professor Will- 

 iamson, and in no one of them could a trace of a diatom be 

 discovered. It has long been suspected by microscopists in- 

 terested in the study of these minute organisms that the 

 Italian observer was misled by the accidental introduction 

 of modern forms somewhere during the treatment. It is well 

 known that, even after repeated Avashings and rinsings of 

 test-tubes and bottles, diatoms will still cling to the sides, 

 and becoming afterwards dislodged, make their appearance 

 in other preparations placed in the same tubes or bottles. 



Revivification of Diatoms. 



M. Paul Petit states that, having collected diatoms at vari- 

 ous times of the year, with their substratum of mud, and al- 

 lowed them to dry in the sun for six or eight months, he had 

 placed them in distilled water well aerated, and found that 

 in four days many of the frustules, which showed before only 

 large brown granules, began to have these granules aug- 



Q2 



