304 THE AMERICAN MONTHLY [Nov 



stant unbroken view of the moving diatom under study. 

 In this wise, there will be no tremor or hitching of the 

 slide, but it may be moved by minute impulses without 

 variation for hours at a sitting. As the field of veiw un- 

 der a i objective is about .02 inch, steadiness will be es- 

 sential. Any condenser, or a hemispherical lens, as an 

 aid to the concave mirror, will give a field as bright as 

 necessary. The concave mirror alone, will answer in the 

 absence of substage condensers of any form. 



"While engaged on these recent studies having a bear- 

 ing on the biology of the diatoms, Mr. Lewis Woolman 

 casually sent me a paper by T. Chalkley Palmer entitled: 

 "Demonstration of absorption of carbon dioxide, and the 

 generation of oxygen by diatoms," being a reprint from 

 the Proceedings of the Academy of Natural Sciences of 

 Philadelphia, February, 1897. In his experiments he 

 made use of the chromogen of logwood, called Hsematox- 

 ylin. He discharged the red color of the liquid Hspma- 

 toxylin by blowing the breath into the solution when the 

 carbon dioxide reaction turned the liquid into a yellow- 

 brown color. While under the influence of nascent oxy- 

 gen, as elaborated by the diatom, the light red hue of the 

 hi^matoxyliu deepens momentarily and ends by becoming 

 a very deep blood red which latter red color may be dis- 

 charged by carbon dioxide. These reactions, as noted by 

 Mr. Palmer, may have a bearing on the action of the liv- 

 ing NaviculsB on the minute yellow or brown particles of 

 wood as previously detailed iu this paper. It is probable, 

 however, that the reactions observed by Mr. T. C. Palmer 

 could be shown fully as well under the microscope, as in 

 the manner indicated in his paper. A number of living 

 diatoms could be watched in the field while immersed in 

 a solution of hiematoxylin before and after treatment 

 with carbon dioxide. Mr. Palmer's paper is condensed 

 into three pages, with a diagram indicating how the test 

 sliould be made. It is stated that he used the non-motile 



