ORDER COPEPODA ; CYCLOPS. 273 



marine. The fresh-water species abound in the muddiest and 

 most stagnant pools, and often too in the clearest springs ; the 

 ordinary water with which London is supplied frequently con- 

 tains great numbers of them. The marine species are to be 

 found, often in immense abundance, in small pools on the sea- 

 shore, within high- water mark, living among the sea-weeds and 

 corallines ; and others inhabit the open ocean, where, by the 

 luminous properties they possess, they assist in producing its 

 phosphorescence. Their vast numbers are the less surprising, 

 when the extraordinary rapidity of their multiplication is known. 

 It has been calculated by Jurine, who attentively observed their 

 habits, that from one female, 4,442 millions of young might be 

 produced in a year. The time occupied in the transformations and 

 development of the young, varies according to the season ; and 

 this variation appears to depend, according to the experiments of 

 Mr. Baird,* not only on temperature, but also on the degree of 

 light, the metamorphosis being retarded by darkness, as in the 

 Batrachia ( 483). The Cyclops is carnivorous, feeding upon 

 Animalcules that are brought to the mouth by the action of 

 the feet-jaws, which create a whirlpool in the surrounding water; 

 and in this manner they even devour their own young. In their 

 turn they fall victims to the larvce of aquatic Insects, the Water- 

 spiders, and other aquatic animals, which thus restrain their 

 multiplication within due bounds. Owing, probably, to the 

 softness of their envelopes, they do not resist drought as well as 

 many other Entomostraca ; but they seem capable of resisting 

 almost any degree of cold, and they ha\;e been immersed for 

 some time in spirit of wine, without losing their vitality. 



811. All these minute Entomostraca furnish very interesting 

 objects for Microscopic examination ; and the study of their 

 development and habits will abundantly repay the most diligent 

 observation. Except during the winter, there is probably not a 

 pool of water in this country, that does not contain some species 

 of them . 



* " Magazine of Zoology and Botany," Vol. I., p. 316. A large proportion 

 of the facts here stated respecting these and other Entomostraca, are derived from 

 Mr. Baird' s highly interesting and valuable papers in that journal. 



