28o AQUATIC MICROSCOPY FOR BEGINNERS. 



Their bodies areplump and oval, or nearly spherical. 

 The skin of most of the forms is soft and easily 

 broken, but in the members of a single genus, Arremi.- 

 rus, the surface is firm and comparatively hard. They 

 are all brightly, even brilliantly, colored. The sur- 

 face may be of one uniform tint, with a few blackish 

 or brownish spots on the posterior region, or the single 

 individual may be variously tinged in different parts 

 of the body. The colors are of almost every imagin- 

 able shade of crimson, azure-blue, yellow, green, 

 brown, gray, or purple. The eight long legs also 

 share in the general brilliancy, and at times present a 

 coloration entirely different from that of the body. 



The eyes are usually on the upper surface near the 

 front border. They are small, and may be either 

 round or crescentic in shape, and red, black, or car- 

 minfe in color. They are from two to four in number, 

 and are usually placed close together, or when four in 

 number, arranged in two distinct pairs. 



The upper part or the back of the little animals may 

 be entirely smooth, densely clothed with short hairs, 

 or with a few scattered, fine bristles. It may also 

 present no markings when magnified, or, as in a single 

 genus, Arrenurus, it may be beautifully ornamented 

 with a network of narrow meshes in an hexagonal 

 pattern. 



In all, or nearly all the mites the upper surface 

 bears two or more black, dark brown, or reddish spots 

 distinct from the general coloration of the body. 

 These are caused by nearness to the surface of the in- 

 testines or of other internal viscera, the dark con- 

 tents of which show their color through the skin. 

 In some specimens these dark spots become large, 



