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for a time, but at last become stationary like their neighbours. The resting state, 
as the name implies, is one of repose, in it they germinate in due course of time, 
after having formed for themselves a thickish envelope. This plan enables them 
to propagate again. It is asingular thing that in this resting state they are vastly 
better for having been allowed to dry up. It seems contrary to our notions that 
fresh water Alge should not be utterly destroyed unless they were under the in- 
fluence of moisture ; but it is a fact that their development does require absolute 
dryness, or if not required it is no earthly disparagement to them. I remember 
a friend telling me, that on a certain occasion, after an absence from home of 
some weeks, to his great disturbance of mind he found, on his return home that 
his servants had tidied up his room, and in doing so had emptied some of his 
bottles ; amongst them was a bottle of Protococcus. After it had been unattended 
to for some weeks, he put some water into it, and to his intense delight and as- 
tonishment, soon found arich colony of Protococcus full of life. Irecollect reading 
somewhere a suggestion, that the Diatomacee are eccentric in their habits. We 
know that they are found in peculiar places, where occasionally they are very dry, 
such as the trunks of trees, the corners of windows in railway carriages, &e. A 
drenching of wet does not suit them in reviving, but a gradual moistening does, 
such as dew or fog. So also many of our snails and slugs are quite dormant in 
dry seasons. If they cannot find a moist cool place, they form a false operculum, 
and so are free from attacks of many creatures which otherwise would prey upon 
them. This false mouthpiece is gradually dissolved when rain comes, and the 
mollusks again become active. So with Protococcus. P. viridis at certain times 
of the year fringes the edges of pools with a green scum, and as the water recedes 
they get that amount of dryness which, so far from being an injury to their life, 
seems to be so highly important to their perpetuity. 
Exactly corresponding to this state of life we find Protococcus pluvialis, in- 
habiting, amongst other localities, the ends of waterpipes, spouts, and gutters, 
which at times, as in the heat of summer, become as dry as bricks, but as soon 
as a shower of rain comes, Protococcus becomes wide awake, and quite ready for 
its mission in life. The ready appearance of Protococcus is extraordinary. In 
houses before their structure is complete, before they are out of the builder’s 
hands, it exists. If it can gain a position anywhere it avails itself of its posture. 
The wind no doubt is a useful agent in effecting this, and conveys it as opportunity 
occurs, to various localities. 
It has been said that Protococcus viridis, when enormously developed, produces, 
under certain conditions, what is known as the red snow, figured by Greville (Se. 
Crypt FL, fig. 231,) as P. nivalis. The word viridis certainly seems inapplicable 
to nivalis, as also does the term red to snow. But it must not be forgotten that 
certain states of Protococcus, although green, do become transformed to red. Dr. 
Harkness, a friend known to most of us, sent me some red snow from the United 
States of America, a few months since: unquestionably, on arrival, it was far 
redder than snow. Not only has the redness faded, but the crusting over the 
plant has considerably thickened, and there is a large preponderance of green 
