Things not generally Known. 



SEKVICES OF SEA-SHELLS AJSD ANIMALCULES. 



Dr. Maury is disposed to regard these beings as having much 

 to do in maintaining the harmonies of creation, and the prin- 

 ciples of the most admirable compensation in the system of 

 oceanic circulation. "We may even regard them as regula- 

 tors, to some extent, of climates in parts of the earth far re- 

 moved from their presence. There is something suggestive 

 both of the grand and the beautiful in the idea that while the 

 insects of the sea are building up their coral islands in the per- 

 petual summer of the tropics, they are also engaged in dispens- 

 ing warmth to distant parts of the earth, and in mitigating the 

 severe cold of the polar winter." 



DEPTH OF THE PKIMEVAL SEAS. 



Professor Forbes, in a communication to the Royal Society, 

 states that not only the colour of the shells of existing mollusks 

 ceases to be strongly marked at considerable depths, but also 

 that well-defined patterns are, with very few and slight excep- 

 tions, presented only by testacea inhabiting the littoral, circum- 

 littoral, and median zones. In the Mediterranean, only one in 

 eighteen of the shells taken from below 100 fathoms exhibit 

 any markings of colour, and even the few that do so are ques- 

 tionable inhabitants of those depths. Between 30 and 35 fa- 

 thoms, the proportion of marked to plain shells is rather less 

 than one in three ; and between the margin and two fathoms 

 the striped or mottled species exceed one-half of the total num- 

 ber. In our own seas, Professor Forbes observes that testacea 

 taken from below ] 00 fathoms, even when they are individuals 

 of species vividly striped or banded in shallower zones, are quite 

 white or colourless. At between 60 and 80 fathoms, striping 

 and banding are rarely presented by our shells, especially in the 

 northern provinces ; from 50 fathoms, shallow bands, colours, 

 and patterns, are well marked. The relation of these arrange- 

 ments of colour to the degree of light penetrating the different zones 

 of depth is a subject well worthy of minute inquiry. 



NATURAL WATER-PURIFIERS. 



Mr. Warrington kept for a whole year twelve gallons of water 

 in a state of admirably balanced purity by the following beauti- 

 ful action : 



In the tank, or aquarium, were two gold fish, six water-snails, and 

 two or three specimens of that elegant aquatic plant Valisperia spora- 

 lis, which, before the introduction of the water-snails, by its decayed 

 leaves caused a growth of slimy mucus, and made the water turbid and 

 likely to destroy both plants and fish. But under the improved ar- 

 rangement the slime, as fast as it was engendered, was consumed by 

 the water- snails, which reproduced it in the shape of young snails, which 



