1899] MICROSCOPICAL JOURNAL 111 



greeu, these being the largest; others, a brownish red, 

 these being the most numerous; and others were hyaline. 



Soon the water became tilled with very minute red 

 spores, actively motile; the larger of these appearing 

 slightly elongated and flattened. After the larger green 

 spores had increased many times in size they began to 

 show ameboid motions. These were evidently develop- 

 ing euglena. The larger brown spores at the same time 

 changed tiieir globular form and showed slight angles and 

 a bellows shape. Was it Surirella ? A smaller kind with 

 a deeper color became rectangular in one position remain- 

 ing circular in the other. These I thought Melosira. 

 Many of the hyaline spores threw out a pointed elonga- 

 tion which made them comet-like in shape. This tail vi- 

 brated like the tail of a tadpole and drove them through 

 the water with considerable activity for a time, but they 

 finally became fixed, their tails retracted, and their chang- 

 ing shapes showed them to be infant ameba which soon 

 grew large enough to attack the red spores. They were 

 so numerous that a drop of sediment placed on a slide 

 would show dozens of them in the field at a time, in any 

 part of the slide. They grew rapidly and committed 

 havoc upon the red spores to which they confined their at- 

 tention. At this time the larger hyaline spores germina- 

 ted and threw out threads of mycelium which soon per- 

 meated the entire mass of sediment, contracting and 

 binding it together and destroying all other life. 



I now cleaned up the whole by the acid treatment. The 

 large abnormal Surirella were completely dissolved, show- 

 ing a total lack of silex. The Pleurosigma had nearly 

 disappeared, but I obtained a considerable number of the 

 newly formed Surirella and Melosira, and made quite a 

 number of slides. About one-third of the Surirella show- 

 ed a curious notch or depression on one side of the valve 

 and the melosira all showed a dot which looked like an 

 opening on one side the centre. 



