246 Prof. Meyen on Red and Green Snow. 



viridis) and the red {Protococcus nivalis) are one and the 

 same plant, only in different stages of development, but that 

 it is difficult to say which of these states is the original. 



Moreover in the red snow there were some red moniliform 

 filaments, which appeared to belong to the order Torula. 



To these observations on the colouring of snow by so-called 

 Protococci, the following addenda may be made. There is 

 now no doubt that the species of Protococcus are true Infu- 

 soria*, and indeed Protococcus viridis and nivalis are nothing 

 more than Enchelis sangiiinea and Ench. Pulvisculus {Euglefia 

 sanguinea and Ei(g. viridis, Ehrenberg) : the appearance of a 

 red dot near the base of the rostrum, which is considered 

 an eye, makes it possible, by means of the present magnifying 

 pov.ers, to judge of this point with certainty. 



The long and rapidly-moving ^/^cAe/if/ej? were not formerly 

 considered as species of Protococcus ; but the above-men- 

 tioned species exhibit at times a perfectly motionless state, in 

 which they appear spherical, and thus they have been de- 

 scribed as Protococci. In this passive state they have been 

 observed by Miiller and Ehrenberg. The former thought 

 them dead ; and the latter says of Enchelis Pulvisculus (' Die 

 Infusionsthierchen, p. 120), that it often becomes suddenly 

 pyriform or spherical without unfolding itself; and that this 

 appears to be the result of uneasiness caused by a che- 

 mical change in the water, which kills it. This explanation is 

 however evidently incorrect : moreover the animalcules are by 

 no means dead when motionless and spherical, but are in a 

 state of development ; they become gradually larger, indeed 

 sometimes fourfold. In such enlarged individuals several 

 small ones are formed, and it is not uncommon to see three, 

 four, five or six, or even more therein ; in Enchelis Pulvisculus 

 these young globules are coloured a beautiful green, and the 

 containing integument consists of a fine and colourless skin, 

 which afterwards disappears. One often sees the red dot on 

 these young globules, and this is a good character to distinguish 

 these formations from small Nostochinea;. M. Martins, it is 

 true, never saw small globules appear on the large green ones 

 of the snow; but he came to the same result, viz. that the green 

 and red snow are formed by one and the same plant (which 

 he holds the vesicles to be), in different states of development. 



It is these spherical, reposing animalcules which often ap- 



* Agardh's Order Protococcus consisted not of EncJielides only ; witli 

 Protococcus viridis was also placed that small green plant which is found in 

 infinite numbers among the so-called Oscillatoria muralis, and which covers 

 harks of trees with a green coating. It is this plant which I have described 

 and depicted as Protococcus viridis (Linnasa of 1827, p. 403. tab. vii. fig. 

 A,l — 4) ; it has often been held to be the original cells of Lichens, and Tur- 

 pin, in ISliS, called it Heterocurpclla qiiadrijuya. — Mey. 



