NOTES ON SOME CANADIAN INFUSORIA. 303 



separated from the posterior portion ; peristome field furrow-like, 

 commencing on left side a little distance from the anterior extremity, 

 produced obliquely downwards towards the right in a groove formed 

 by the oblique curvature of the body, and terminating in a short 

 pharynx at or shortly past the middle line ; on the contraction or 

 shortening of the body, the peristome with the pharynx lor the time 

 describes a complete spiral circuit, the animalcule presenting in this 

 condition a totally different aspect ; anal aperture postero-terminal ; 

 contractile vesicle single, posteriorly located. Inhabiting salt and 

 fresh water." 



With this definition of the genus my observations, although identi- 

 cal in most particulars, do not exactly correspond. The points on 

 which I differ are mainly the position of the anal aperture, and the 

 number of contractile ves : cles. On reference to the figure (PI. 

 fig. 1), it will be seen that I have represented the anus (a) as being 

 postero-lateral, and I have done so only after having witnessed the 

 emission of unconsumed food from that point. Claparede and 

 Lachmann 1 did not observe the anus, but mei'ely suppose it to be 

 situated posteriorly. Stein, 2 however, distinctly states that it is 

 postero-terminal, and on his authority it is so described above. As 

 to the contractile vesicles, I have observed two, one situated in front 

 of the pharynx (a. c. v. J and the other (p. c. v. J near the posterior 

 extremity but not quite central. On first observing the form I did not 

 see the anterior vesicle, probably on account of the constant rotation 

 about their long axis which the animals performed, and which, as 

 the vesicle is situated slightly in front of the junction of the over- 

 lapping anterior portion with the posterior one, would render it liable 

 to be overlooked. I, however, lately observed it in one form, but 

 having lost it, and having not as yet discovered another, 1 am unable 

 to confirm the observation. I would then alter these points of the 

 generic definition so as to read, "anal aperture posterior ; contractile 

 vesicle single or double." 



The only species belonging to this genus that I have been able to 

 find reference to is M. sigmoides, and for it the genus was formed. 

 The descriptions of this form vary somewhat, but in no particular 

 sufficiently important to establish a new species. The characters of 



1 Etudes sur les Infusoires et Rhizopodes. 1858-1S60. 

 a Der Organismus der Infusionthiere. 



