No. 467] ZOOLOGICAL MATERIAL. 781 
While the Amoebz usually disappear from such a culture in a 
short time, occasionally they persist for a week or more, grow- 
ing larger. In some cultures they seem to encyst or disappear 
almost entirely, and later reappear in considerable numbers. 
Hence old cultures should be watched, and retained until they 
become overgrown with fungi and hence worthless. 
The advantages of the Ceratophyllum method, as described 
and used by Jennings, are that it gives Amoebe in abundance, 
at the time desired, with almost absolute certainty. But the 
Amcebz obtained by this method are seldom large ; their devel- 
opment is often interfered with and they usually give place to 
other organisms before attaining maturity. Moreover, the pres- 
ence of an excessive amount of bacteria and other organisms 
often obscures the Amcebze, and makes it difficult to find and 
study them. To overcome these difficulties, the writer, aided 
by a suggestion from Professor Reighard, devised a modification 
of the above method which has proved a valuable supplement to 
it. 
As soon as Amoeba appears in the Ceratophyllum cultures, 
skim off the brown scum with a spoon, and put it in small bac- - 
teria dishes about four inches in diameter and one and one half 
inches deep, with enough water to fill the dish about one inch 
deep. Add a little of the decaying vegetable material from near 
the surface of the Ceratophyllum cultures. This should be done 
several days before the Amæbæ are desired for use. Cover.the 
dishes and keep them in a warm place, but not in direct sun- 
light. In a few days Amoebee will be found in abundance in 
some of these cultures, in the scum at the surface or in the ooze 
and on the decaying plant material at the bottom of the dish. 
Some of the cultures prepared in this way by the writer gave 
results far better than were obtained from the ordinary Cerato- 
phyllum cultures; the specimens were remarkably large, active, 
and numerous. The Amoebz pass through stages of develop- 
ment and sometimes practically all of them in a given culture 
encyst at the same time. They may reappear later in an active 
stage. Later on, among other organisms may appear in these 
cultures Arcella, Chilomonas, Parameecium, Vorticella, and occa- 
sionally some colonial Protozoa. : : 
