INFUSORIA AND OTHER ANIMALCULE. 245 



It is our hope to have a telegraphic cable, uniting 

 us with the continent of America, imbedded one 

 day in such a rock, where it would lie securely for 

 ages. (See Fig. 37.) 



The rapid and mysterious transition of colour 

 which is observable in lakes, and which has often 

 created alarm in the minds of the superstitious, 

 has been attributed* to Infusoria. A lake of clear 

 transparent water will assume, for instance, a green 

 colour in the course of the day; it will become 

 turbid or mud-coloured about noon, when the sun 

 brings the Infusoria to the surface, rapidly develops 

 them, and where they die by millions before night. 

 Microscopic vegetables (Algae,, etc.) may produce 

 similar effects. Similar phenomena are observed 

 in salt water ; hence, probably, the Red Sea and 

 Yellow Sea derived their names. Certain Astaria 

 and Euglena ruber give to water a blood-red colour. 

 The same happens when microscopic Algce, of a red 

 tint, found at certain seasons in the Bed Sea, are 

 present. Euglena viridis, Cryptomonas glauca, Monas 

 bicolor, and other Infusoria, colour water intensely 

 green. A blue colour will be observed when con- 

 siderable quantities of Stentor ceruleus are present, 

 and yellow with Astaria flavescens and Stentor aureus, 

 etc. Of these the green and red tints are the most 

 frequently seen in nature. 



* By Pritchard and others, 



