Coincidently, (was it consequently?) a greenish tinge pervaded the
water, speedily increasing in depth and opacity. In five days, no object
could be discerned six inches from the glass, and my beautiful Aquarium
was transformed to an unsightly ditch.
Yet the water was apparently pure, and the activity of its inhabitants
was in no wise lessened. What was this vexatious greenness? Was it
animal or vegetable? Was it the diffused spores of the perfected
Enteromorpha or of the rank Confervae upon the stones? If neither, what
was its cause?
Excess of light was the most obvious suggestion; and so it was supposed
that its exclusion might be a potent remedy. Therefore a double curtain
of glazed muslin was stretched across the window; and the tank, both top
and sides, wrapped in folds of paper. A week of darkness changed the
deep green to a dingy olive. But the experiment could not be continued.
The nightly admission of air by lifting the paper covering was
insufficient to maintain the imprisoned creatures. They were happy,
though captive, while in a mimic ocean, but miserable in a dark dungeon.
Languid and spiritless, they lay supine, or crawled listlessly and
aimlessly about. This would not do, and so light was again admitted
freely to all but one side of the tank; there, a screen of yellow paper
intercepted the direct rays of the sun, while upon the top they fell
through the foliage of a Clematis vine.
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