T, 



620 Fresh- Water Entomostraca. [October, 



the ascogonium is filled up by the loose tissue of the inner rami- 

 fications. 



The ascogonium is divided by repeated partition into a number 

 of asci, each of which in our species contains eight spores. 

 According to the observations of several botanists, these spores 

 are not developed before the next spring, so that the parasite is 

 preserved through the winter by means of the peridia. In most 

 species of Erysiphe these peridia are provided with hyaline 

 appendages, some of which are of wonderful regularity and 

 elegance of form, when seen under the microscope. 



:o:- 



FRESH-WATER ENTOMOSTRACA. 



BY C. L. HERKICK. 



THE collector of fresh-water specimens is constantly meeting 

 unexpected forms, especially among the smaller organisms, 

 and of these no order of animals furnishes a wider variety or 

 more curious adaptations than the fresh-water Crustaceans em- 

 braced in the old group Entouwstraca, which is by many authors 

 at the present day subdivided into several orders of Crustacea, 

 the name being retained for a single order. To the microscopist 

 particularly they are available as a never-failing field for study, 

 since a cup of water from almost any source will contain abun- 

 dant material for a day's work. 



The Entomostraca have specialized jaws, but the gnathites never 

 exceed three pairs. The segments of the abdomen are devoid of 

 appendages. The name was derived from two words, meaning 

 insect and shell, by Otho F. Miiller, and applied by him in his 

 "Entomostraca" (1785) to the animals which had hitherto been 

 all comprised in Linnaeus' genus Monoculus, named from the sup- 

 position that they possess but one eye. This order has, gener- 

 ally speaking, been much neglected, and in America particularly 

 it seems to have escaped attention. The members of this order 

 are never large, and many are so small as to be with the greatest 

 difficulty detected by the unassisted eye, yet from their great 

 variety, wide range and immense number they assume a j)osition 

 of considerable importance in the animal kingdom. 



Recent investigations instituted by Mr. S. A. Forbes, of the 

 Illinois State Laboratory of Natural History, have emphasized 

 the fact that the lowly animals play important parts in the econ- 

 o:in' of nature, he hav'in<j found that these Crustaceans ciitir 



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