302 NOTES ON SOME CANADIAN INFUSORIA. 
perature, reappearing when the temperature increased, the ova 
apparently not being affected at a temperature which destroys the 
adult animal. This is a well-known phenomenon, and is exemplified | 
by many of our Insects, which perish in the Fall, but whose eggs are 
able to withstand the intense cold of Winter. These same remarks 
apply to the Rotifer Philodina citrina, which was also present in 
considerable numbers. A single Nematode worm, which I did not 
identify, and several examples of a Planarian were seen, the latter 
possessing a distinctly vacuolar parenchyma. Of the lower forms of 
life many examples were observed: Arcelle, especially A. dentata, 
Amebe, Actinophrys sol, and many Flagellata. Of these the Arcelle 
persisted through all the changes, the Ame!ce perished in low tem- 
peratures, and Actinophrys, having only appeared lately, has not been 
exposed to cold. 
With these preliminaries I shall now pass on to my observations 
on certain Infusoria, which I regret are somewhat incomplete, owing 
both to lack of sufficient time to perfect them, and more especially 
to the want of the necessary literature, which, for efficient work, 
shoud be continually at hand. 
METopus, nov. spec. 
The genus Metopus was originated by Claparéde and Lachmann 
for the reception of a species formerly described by O. F. Miiller as 
Trichoda sigmoides, and by Perty as an unknown form. It presents 
many peculiarities, and has hitherto been frequently mistaken for 
other forms ; Balbiani, for instance, mistaking it for the young form 
of Spirostomum ambiguum. It has been described from several 
localities in Europe, Claparéde and Lachmann having found it at 
Berlin, Englemann at Leipzig, Stein at Tharand and Niegmegk (very 
numerous among Lemna polyorrhiza and trisulca), and Balbiani at 
Paris, but as far as I can ascertain it has not yet been described from 
America. 
The characters of the genus are thus given by Kent’: “ Free- 
swimming, highly elastic and changeable in shape, normally elongate, 
oval, or fusiform, rounded at both extremities, cylindrical or only 
slightly flattened; the anterior portion usually twisted obliquely 
towards, and overlapping the left side of the ventral surface, sharply 
1 Manual of the Infusoria. London. 1882. 
