cO4 NOTES ON SOME CANADIAN INFUSORIA. 
the form which I observed differ so very considerably from those of 
M. sigmoides, that I think it necessary to regard it, however, as a 
new species, M. sigmoides is described by Claparéde and Lachmann 
as having the buccal fossa bounded by cilia much more vigorous than 
those of the rest of the body.- In the digestive cavity anteriorly are 
constantly found a number of granules, highly refractive, whose 
signification is still problematic, and which recall very strongly those 
found frequently in Paramecium Aurelia, and in certain Nassule. 
The contractile vesicle is spacious, and lodged in the posterior half of 
the body, which is S-shaped. In the figure they represent the 
nucleus as a morula-like structure. Engelmann! describes it thus: 
“Tt reaches a size of only 0.15 mm., posteriorly is bent towards the 
right not quite S-shaped, possesses at the posterior extremity some 
long bristles and at the centre of the body a usually curved reniform 
nucleus. Metopus possesses an adoral row of cilia of short bristles, 
which are however in a strange manner fastened not on the upper 
but on the lower side of the long peristome field. The upper border 
of the peristome bears the usual cilia, as well as the whole anterior 
half of the body.” Engelmann’s form accordingly differs from that 
of Claparéde and Lachmann in the possession of terminal sete, 
which are neither mentioned by the latter authors in the text, nor 
represented in their figure; also in the absence of the highly refrac- 
tive bodies, and in the shape and appearance of the nucleus. Stein, 
again, describes this same form as occurring in three distinct shapes — 
the normal, described above, the shortened, and the rolled up; and 
also describes a bunch of terminal sete anda terminal anus. He 
criticises Claparéde and Lachmann’s figure somewhat harshly, point- 
ing out the non-pourtrayal of the proper curvature of the posterior 
portion of the body, and the incorrectness of the structure of the 
peristome and the nucleus, and the absence of the terminal bristles. 
He evidently does not recognize the possibility of the form observed 
by the Swiss authors being different from that he describes. 
The form I observed differs from these descriptions in many 
respects, and the various differences may be discussed serially. 
(1) The twisting does not appear to be us extensive as described 
for M. sigmoides. On examining the figures of C. and L. it appears 
that the plane of the anterior half of the body is parallel with that 
1 Zeit. fiir Wiss. Zool. XI. 1861. 
