234 
Malcolm E. Stickney 
material may be at hand. The writer wishes to express his deep 
indebtedness to Prof. S. J. Holmes, of the Department of Zoology, 
University of Wisconsin, who very kindly furnished the material 
upon which this work was based, and whose suggestions in connec- 
tion with the work were most helpful, and to his friend and, 
pupil Miss Gertrude Lett, who made all the drawings here included. 
For two years past Spondylomorum quaternarium Ehrenb. has 
been observed at Madison, Wisconsin, coming in in great numbers 
in aquaria containing old grass and dead leaves brought in from 
rain pools in early spring. The organism begins to make itself 
evident in such aquaria about ten days after the culture is started, 
rapidly increases in numbers for a few days, until portions of the 
aquaria are fairly green with masses of individuals, and then as 
gradually the culture dies out. All attempts to rear these organ- 
isms in the laboratory, other than in the above sporadic fashion, 
or to keep the cultures running for any length of time, have so 
far proved fruitless, although no more than tentative efforts to do 
this were made. The strong positive phototaxis which these organ- 
isms show makes their separation from the infusoria and bacteria of 
the culture water a very simple thing. By carefully transferring a 
pipette of material taken from the side of the aquarium illuminated 
by direct sunlight, to the shaded side of a small vessel of sterile 
water, and then almost immediately withdrawing a fresh pipette- 
ful from the sunny side of the latter vessel, and repeating the pro- 
cess once or twice, a pure culture of Spondylomorum is readily 
obtained. 
For the study of the grosser features of habit a method of prep- 
aration was employed which was suggested by Dr. Marquette of 
the University of Wisconsin in his work on the antherozoids of 
Marsilia. A drop of water containing a large number of individ- 
uals was placed on a clean slide and exposed to the fumes of osmic 
acid for a few minutes and then evaporated to dryness, thus fixing 
the organisms to the slide. The preparations were then stained 
with an aqueous solution of pyoktanin blue until the cilia were 
clearly brought out, when they were washed with water, again 
dried without heat, and mounted in benzole balsam. With rather 
dense organisms containing small vacuoles this method has proved 
very successful, as the contraction due to drying is slight, and 
certain details, including the cilia, are brought out with great 
clearness. Preparation of Spondylomorum made in this way show 
