260 Phillips on a Comparative Study of the 
the depth of the drop, which would carry the plant beyond 
the focal distance of the objective. At least this has been 
the difficulty experienced in trying to follow Zukal’s obser- 
vations on living material in the present investigation. 
Nadson’s work (57) was principally performed upon 
Merismopedia elegans, Gloeocapsa polydermatica, Lyngbya 
curvata, Oscillaria (several undetermined species), 4 phano- 
capsa Grevillei, Chroococcus turgidus, Tolypothrix ega- 
grophila, Aphamzomenon flos aquae, and for comparison, 
the bacteria Clostridium butyricum and Cladothrix dicho- 
toma. For the purpose of fixation he found iodine-alcohol 
the most useful, also a saturated aqueous solution of corro- 
sive sublimate. Hzematoxylin was his chief stain, though 
vesuvin, iodine green, a mixture of methyl blue and fuchsin, 
and acid carmine were also used. Intra-vitam staining 
with methyl blue was also productive of good results. Most 
of his conclusions on fixed material he was able to verify 
on living specimens, thus obviating the possibility of mis- 
taking artifacts for normal structures. Micro-chemical reac- 
tions did not give him any definite results and were there- 
fore discarded. A colorless, amceboid central body, occupy- 
ing most of the cell, was found, distinguished peripherally 
by phycochrome from a colorless outer layer, though this 
latter was not to be regarded as a chromatophore, but rather 
as protoplasm. In one form (Aphanizomenon) vacuoles 
were found between the central body and the protoplasm. 
The cytoplasm had a vesiculated structure like the “waben- 
bau” of Biitschli, and the chlorophyll and phycocyan were 
contained in the walls of these vesicles. The central bodies 
were not always surrounded by the protoplasm, but in some 
filamentous forms (Tolypothrix, Aphamzomenon) they 
reached from end wall to end wall, thus forming a longi- 
tudinal band along a row of cells. The central body had 
the same vesiculated structure as the protoplasm, but was 
not so well defined, the vesicles being filled with a peculiar, 
deeply staining substance which the author called “filling 
