MINUTE STRUCTURE OF PELOMYXA PALUSTRIS. 301 
a more or less ring-like fashion. I was not able to detect any 
appearance of nuclear division. The radiate alveolar layer 
round the nuclei and refringent bodies has been noticed 
above. 
The Bacteria. 
The rod-like bodies found in profusion in Pelomyxa were 
originally described by Greeff as “crystals,” but later observers, 
firstly Bourne, and after him Pénard (loc. cit.), have been 
inclined to regard them as symbiotic bacteria. Leidy (‘ Fresh- 
water Rhizopods of N. America, 1879’) and Greeff both 
thought they distinguished a “ transverse striation’’ of the 
rods. 
M. Pénard considered the rods as “ véritables bactéries.” 
He saw in them “une striation transversale, ou plutdt une 
apparence de divisions 4 intervalles réguliers, telles qu’on 
les trouve dans les algues filamenteuses inférieures.’’ With 
reagents the rods appeared “‘nettement divisées en plusieurs 
parties par des étranglements,” or “ reduites en quelque sorte 
a des chapelets, dont les nombres respectifs de grains étaient 
de 2, 3, ou 4.” But he did not make it very clear whether 
the appearance he saw was one of constriction merely and due 
to reagents, or jointing, which is rather a different thing. 
Nor did he state definitely the largest number of divisions 
seen in a single rod, while his description of some of the 
longest as “ filaments ondulés ou recourbés” rather inclines one 
to think that some of those he saw might have been really the 
“algues filamenteuses” to which he compared them, and 
which are not uncommonly found in the protoplasm of 
Pelomyxa. The rods, as figured in the plate accompanying 
M. Pénard’s paper, show either transverse striation or a 
moniliform appearance ; the former does not of course amount 
to jointing, and the latter is very different from anything seen 
by me. 
In a Pelomyxa killed with osmic acid, stained in bulk with 
carm-alum, and teased up in glycerine, I found that the 
rods were not constricted, but very distinctly jointed 
