^8 THE AMERICAN MONT'HLY [Mar 



these ditches and the brook is coated with a yellowish 

 brown film composed of living diatoms. These were 

 chiefly Pleurosigma americanum, P. hypocampus, P. breb- 

 bissonii and P. fasciola, with myriads of minute species. 



I have previously published accounts of attempts at the 

 cultivation of such finds of diatoms, which attempts all 

 failed from the same cause, the rapid development of de- 

 structive animals which devoured them. I examined this 

 film at different points along the brook and the ditches 

 for more than a mile in length. It varied considerably 

 in different places, at one point it was a yellowish green 

 from the presence of vast numbers of Euglena. It proved 

 to be the most extensive continuous film of living diatoms 

 I had ever seen not even excepting the extraordinary one 

 at Shell Beech, Leete's Island, that I described some 

 years ago. I visited Leete's Island in the autumn of that 

 year and found the film of diatoms had disappeared, but 

 late in August, 1895, the film was still conspicuous at 

 West River, and it occurred to me that as my experiments 

 were all tried during warm weather, another trial in cold 

 w^eather might have a different result. Accordingly, in 

 September, I appeared' on the ground with a large basket 

 loaded with glass bottles, a jointed fish-pole and other 

 apparatus. About a dozen of these were quart bottles and 

 square, to pack closely. I filled one of these from the R. 

 R. tank, getting an abundance of Artemia gracilis. Then 

 fastening a tablespoon on the end of my fishpole, I scoop- 

 ed up a quantity of the film of diatoms from various points 

 along the ditches and from the brook, filling up each bot- 

 tle with water from the same place from which I took the 

 diatoms. After about three hours work I had collected 

 nearly four gallons of saltwater and diatoms which I 

 thought abundant for my experiments. At home I poured 

 out this material partly into glass dishes and partly into 

 brown earthen bowls which I procured for this purpose. 



As I had frequently noticed that the occurrence of these 



