No. 4.] OSLER — BIOLOGY NOTES. 251 



BIOLOGY NOTES. 



By Professor Osler, M.D., McGill College. ^ 



X. — On a remarJcahle vital phenomenon observed at Lake 



Memphremagog. 



During; the first week in September, 1881, the water of the 

 lake presented a peculi;ir appearance, owing to a number of" min- 

 ute green particles floating in it. In places they were so thickly 

 crowded together that the water was of a deep green colour. 

 Except near sliore, they did not float on the surface but were dif- 

 fused through the water to the depth of several feet. It was sug- 

 gested to me by a friend that they were pollen grains, but their 

 diffusion through the water and the season of the year seemed 

 against tliis. They looked not unlike Volvox glohator, but I 

 have never seen this alga in such profusion. Fortunately, I had 

 my microscope with me and the question was soon settled. Each 

 little o-reen mass formed a ixelatinous ball, about one-thirtieth of 

 an inch in diameter and enclosed numerous unbranched beaded 

 filaments and proved to be a Nostoc — Nbsfoc minutissimum — a 

 minute confervoid alga met with in water and in moist places. 

 It is !iot a very uncommon species in our ponds, the remarkable 

 point is the extraordinary profusion in which it occurred. The 

 Noatoc annmune is plentiful in the ponds at the Mile End, form- 

 insr irreg-ulir u;re('n balls the size of a horse-chestnut. 



The Nostoc folia ceuiii also occurs there; it has a membranous 

 somewhat folded frond, usually growing erect on damp clay. 



II. — On the occurrence of Ophrydium versatile. 



This infusorian is met with in many of our lakes, particularly 

 those to the north of the St. Lawrence. Its macroscopic characters 

 are pl.mtlike as it forms irregular greenish masses of a gelatinous 

 consistence and though usually somewhat flattened, they may occur 

 as beautiful j^lobular bodies of a liuht srreen color. At Lac a I'eau 

 Claire, in the propei ty of Mr. G. W. Stephens, I found one mass the 

 size of a l.irge apple. On examination the gelatinous substance is 

 seen to be colorless bnt imbedded in its cortex are numerous green- 

 ish infusoria with very extensible spindle-shaped bodies which are 

 anchored by a delicate terminal filament in the matrix. When 

 extended the body measures about one-hundredth of an inch, 



