226 THE AMERICAN MONTHLY [Au 



this fact lends support to the view that the order \» not 

 very coherent." 



"The geographical distribution of the marine forms is 

 principally in the temperate waters of the ocean, more 

 abundantly in coastal waters than far from land. Vast 

 banks of Ceratium occur on the British coasts, causing the 

 waters to be brightly luminous at night. They form, with 

 the Diatoms, a very large proportion of the primary food 

 of marine animals. The occurrence of Ceratium tripos in 

 Catenna has been observed only in the open ocean, far 

 from land. In coastal waters they occur separately." 



The genus Pyrocystis contains two very different forms. 

 One is a sphere and the other a form made of two conical 

 pyramids attached by the bases of the cones, something 

 like a Closterium. The first, J. Murray calls Pyrocystis 

 noctilaca and the latter P. fusiformis. The first is lumin- 

 ous at night. It is a tropical form, and to it was attribu- 

 ted the most brilliant displays of luminosity of the sea 

 during the Challenger Expedition. We must remember 

 that when it was first found. Dr. John Murray thought it 

 was a diatom and so announced it. But it does not have 

 any hard skeleton or markings, though from that it can- 

 not follow that it is not a diatom for some diatoms are 

 known which have no hard skeleton or markings. But it 

 is not a diatom at any rate and is ranked until its place 

 can be determined among the Peridinieae. 



Notes on Microscopy. 



F. SHILLINGTON SCALES, F.R.M.S. 



Postal Microscopical Society. — During the summer 

 of 1873, a letter appeared in Science-Gossip suggesting 

 that if twelve gentlemen could be found willing to co-op- 

 erate in forming a little club for the circulation of micro- 

 scopic slides, and notes thereupon, it might lead to a very 

 pleasant and profitable interchange of thought and study. 

 This letter was replied to by the late Mr. Alfred Allen, of 



