10 THE AMERICAN MONTHLY [Jan, 



aifects the photo-salts in the space between the two lines 

 and this is done by diffusion and irradiation. 



We are promised some criticisms of Gates' methods for 

 February and desire others. 



Amoeba in Winter. 



By W. E. DEEKS, M. D. 



During the summer they can be obtained by scraping 

 the under surface of a floating weed or in the superficial 

 ooze along the bottom of any fresh-water pond. In win- 

 ter we need aquaria, and of these a certain amount of 

 care is necessary to keep the forms in a living condition. 

 The most suitable temperature for them is between 45 

 and 70 degrees F. — a sufficiently low temperature which 

 will also prevent the bacteria of putrefaction from devel 

 oping too rapidly. Along with them are usually found 

 the Heliozoa, the stalked Ciliata and some of the Flagel- 

 lata. If the temperature is raised to about 80 degrees 

 F., they quickly disappear and in their place countless 

 numbers of the free-swimming Ciliata make their ap- 

 pearance. The water also becomes putrid. 



In the Autumn the superficial ooze from some fresh 

 water pond is skimmed and placed in a dish, the mouth 

 of which is covered almost completely to prevent too 

 rapid evaporation. Along with the ooze get some decay- 

 ing vegetable matter and also some living water plants^ — 

 Anacharis, Chara and some other common forms will do. 

 A considerable quantity is necessary to keep the water 

 fresh. The aquarium is then placed in a place where 

 there is plenty of light (though preferably not direct sun- 

 light), and in a cool place, bes*^. about 60 degrees F. This 

 then can be left any length of time, and when they are 

 required, by squeezing a little of the decaying vegetable 

 matter on a glass slide, I have never failed to find one or 

 more. 



