MINUTE STRUCTURE OF PELOMYXA PALUSTRIS. 308 
New Species. 
If further criticism of M. Pénard’s observations on Pelo- 
myxa be permissible, it would seem that he has scarcely 
sufficient grounds for the establishment of a new species 
(P. beleosteii). He does not mention any definite feature 
which is not equally characteristic of P. palustris. Size 
is no criterion, since individuals of P. palustris vary very 
much in this particular, as also in the presence or absence of 
sand débris in the protoplasm. The sole real difference appears 
to be in the structure of the nuclei; but as this also differs in 
two nuclei from the same animal (according to the figure), 
and both of these, from their thick walls, size relative to the 
vesicles, and general appearance, bear far more resemblance 
to food-vacuoles with contents than to the nuclei of any 
amceba, it would seem doubtful whether they were really nuclei 
at all. In a paper published several years ago in the ‘Archives 
Exp. de Zoologie,’ Korotneff has given reasons for recognising 
a second species of Pelomyxa. I have no doubt that the form 
studied by me is the P. palustris of Greeff. 
ADDENDUM. 
November 10th, 1893. 
In order to furnish, if possible, a conclusive proof of the 
organic nature of the so-called “ rods” of Pelomyxa, Professor 
Lankester suggested to me that I should attempt to obtain a 
cultivation of these organisms by means of the usual bacterio- 
logical methods. This I did during June, 1893, and the 
following is a short account of the work. 
The investigation was carried on in the laboratory of the 
Regius Professor of Medicine in the University Museum, with 
the kind collaboration of Dr. Ritchie, who was then, and is at 
present, engaged in bacteriological research. 
We made a large number of cultivations by teasing up fresh 
specimens of Pelomyxa in sterilised water, after removing 
them straight from the pond water in which they were kept, 
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