

1901] BRIEFER ARTICLES 203 
was certainly one of the most instructive facts brought out during the 
course of my observations..— JOHN W. HARSHBERGER, University of 
Pennsylvania. 

SWARM SPORE FORMATION IN HYDRODICTYON 
UTRICULATUM Ror: 
1. The methods of fixing were by means of Merkel’s fluid and a 
mixture of iridium chlorid and acetic acid according to one of the 
following formulae: 
(1) Eisen. Iridium chlorid Se 5 BER cent. austere oh a a - 100° 
lacial acetic a - ee 
(2) Iridium chlorid (1 per she oars solution) - - - 100% 
ce 
Glacial acetic acid - - - 
The best results were obtained with the stronger iridium chlorid 
mixture. 
2. There is no differentiated chromatophore in the cell. The 
pyrenoids and nuclei are scattered irregularly throughout the cyto- 
plasm and the chlorophyll is contained in the whole cytoplasmic body. 
The nuclei in both the resting and dividing stages show the structure 
typical of higher plants and are not to be taken as types of primitive 
nuclei. 
3. Cleavage takes place by means of surface constriction of the 
plasma membrane on the outside and the vacuolar membrane on the 
inside of the protoplasmic Jayer. The process is a progressive one, 
the cleavage furrows cutting out first large irregular multinucleated 
masses of protoplasm, which are in turn divided into smaller masses, 
until each contains a single nucleus, the entire protoplast thus being divi- 
ded into spores. The swarm spores are uninucleated biciliated cells. 
At the base of the pair of cilia there is a clearly defined basal body. 
A ‘detailed description of the processes outlined above will be pub- 
lished soon in a more complete form.— H. G. TIMBERLAKE, Cniversity 
of Wisconsin. 
4 One of the best methods of procuring material for microscopic study is to remove 
the protoplasm by scraping, and then to place portions of it on slides fitted into the 
bottom of Petri dishes provided wit mei filter paper. In an hour or two these 

mounds of protoplasm will have spre to permit of their 
examination, At my suggestion, Dr. Mazijck Ravenel, Sy cecrlalogiet of the Pennsyl- 
vania Live Stock Sanitary Board, tried to grow the plasmodium upon ‘eben agar, 
and upon filter paper saturated with bouillon, but failure resulted in both cas 
5Rés of results presented at the me of the Western Naturalists at the 
Hull inka Laboratory, December 27, 1 
