Page:The Zoologist, 4th series, vol 6 (1902).djvu/135

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recent years a great impulse has been given to the study of Crustacea by the numerous expeditions sent out more or less expressly for the purpose of deep-sea exploration. As the result of voyages carried out in rapid succession through the last forty years, a host of forms distinguished for novelty, queerness, or beauty have contributed interest and animation to the pursuits of the carcinologist. The species popularly attractive have for the most part, though by no means exclusively, belonged to the Malacostraca. But during the same period in which the higher marine Crustacea have been thus decidedly making their mark, it happens that in a quite opposite direction the fresh-water Entomostraca have found their way to a modest celebrity. Though not many of them are of any considerable size, they attain in various ways to economic importance by their astonishing abundance. Of those that can be easily captured in almost any pond or ditch the variety is very considerable, and the number of species obtainable can be largely increased by a little extra exertion, without any appeal to imperial resources. Apart from ordinary methods of fishing for them at the sides or in the centre of pools and watercourses, that which more than anything else stands in antithesis to the costly labour of dredging and trawling in submarine abysses is the process, applicable at least to many fresh-water Entomostraca, of dredging on dry land. Many sheets of water at certain seasons completely evaporate, and expose a moistureless floor. If earth be taken from this and placed in water, under suitable circumstances of temperature, there is a good prospect that a crop of Entomostraca will be raised from it. The secret is that crustacean eggs have been deposited in the soil, and have there been biding their time till conditions appro-