NOTES AND MEMOEANDA. 
A New Organ (?) of the Rotatoria. — Dr. Pelletan writes in the H 
‘ J oiirnal do Micrographie,’ that having for several years undertaken .fl 
a series of researches on the Eotatoria, and particularly on the K 
Rotifers, he has come to the conclusion, that these beings are very 
insufficiently known, and that many observations, particularly abroad, || 
seem to have been embellished by their authors so as to resemble 
somewhat a romance. 
“ In January last I found in some Zygnema, which I had preserved : 
in an aquarium for nearly a year, a great number of rotifers without 
eyes, furnished with two rotatory lobes of small dimensions, with 
mastaces of numerous small teeth, and which seemed to me to be the 
Callidina elegans of Ehrenberg. A singular detail struck me. One 
of them had on the flank of the long segment that may be called the 
abdomen, a small hyaline vesicle with a double outline, which did not 
disappear whatever movement the animal made. I considered it at 
first a parasite, and I pressed a little on the covering glass in the 
neighbourhood of the rotifer in order to try and detach it. Not far 
from it two other animals of the same species, which not long pre- 
viously presented nothing abnormal, had now each a vesicle, but one 
had it on the right and the other on the left of the abdomen. With 
a j%- objective I established in the clearest manner that these rotifers 
carried on each side of the body one and perhaps two stigmata. 
These stigmata opened and shut as if by a sphincter ; they were 
placed on the summit of a little papilla, situated towards the lower 
third of the length of the abdomen. When shut they appeared like a 
point surrounded by a circle, indicating a subjacent vacuole, and 
bordered by small radiating wrinkles, formed by the integument con- 
tracted by the sphincter. When open they presented a festooned 
border with a clear bottom. I saw them open and shut alternately 
under my eyes, like the contractile vesicle of a Paramecium, but 
without regular rhythm ; the contraction appeared to me to be volun- 
tary. Seen in profile they constituted a perforation of the integument, 
and the hernia of the subjacent vesicle by their meatus consequent on 
the compression, clearly proved to me that the meatus opened to the 
exterior. As many times as I wished I was able to establish this 
phenomenon and to cause the hernia. This when produced did not 
return any more, at least for several hours, and when the animal 
contracted itself into a ball the hernia persisted. 
It is possible that the fact has already been established, but I am 
not aware of it. I have inferred from it that the mode of respiration 
amongst the different species of rotifers has been insufficiently known 
to me, for these stigmata or stomata belong evidently to the respira- 
tory apparatus, and seem to me to have no other end than to admit 
the aerated water through the thin walls to act upon what may be 
called the hematose, without the intervention of aquiferous canals, 
since the vesicle constitutes a close cavity. 
It was important to verify the number and exact situation of these ^ 
