110 THE AMERICAN MONTHLY [Apr 



Experiments in the Artificial Culture of Diatoms. 



William A. Terry. 



It was now the middle of winter, and wishing to hurry 

 matters, I filled a small teacup with water from one of 

 the cultures and drew up carefully a quantity of diatoms 

 with as little sediment as possible and placed them in a 

 west window in my room where they were exposed to af- 

 ternoon sunlight and a day temperature of about 60 ° F. 

 At night they were cold, in fact sometimes the water was 

 partially frozen. I hoped that this would discourage the 

 animals, but it was a failure in this respect, as eels, 

 ameba and ciliata appeared in increasing abundance. 

 Still, I had an opportunity to note some peculiarities, 

 There, were in this*lot a number of Surirella striatula of 

 the open water type, more like Van Heurck's drawing 

 than that of Wm. Smith. I shall have occasion to note 

 these differing types further on. I soon began to find 

 abnormal forms among these. Sometimes one end would 

 be imperfect and sometimes the other, but more had one 

 edge of the frustule bent in. Whether these abnormal 

 forms were produced by division in a fluid deficient in si- 

 lex, or whether they were older valves in process of solu- 

 tion I felt uncertain, but as the diatoms were rapidly di- 

 minishing in numbers, I determined to attempt to destroy 

 the animals without killing the spores which might be 

 present. Accordingly, I allowed the water to freeze 

 solid, freezing and thawing a number of times in succes- 

 sion, then let the water evaporate until the salt crystal -- 

 ized, filling up again suddenly with fresh-water. This 

 treatment destroyed the animals and also the diatoms, 

 and the amount of sediment was increased. In this sedi- 

 ment soon appeared minute globular bodies which I call- 

 ed spores. These were of many species and soon similar 

 kinds congregated together in separate masses and grew 

 rapidly in size and numbers. Some were of a bright 



