body is very highly arched, in others it is rather flat. The body ia 

 not divided into cephalothotax and abdomen as we find in the 

 spiders. The skin in some species is soft, in others hard. It 

 may be smooth, finely or coarsely lined, or papillated ; some are also 

 provided with more or less porous plates on the dorsal or ventral 

 surface. In the hard-skinned mites, like the species of the genus 

 Arrhcniiriis, for instance, the colouring appears to be in the skins. 

 The colouring in these cases is easily preserved. But in the 

 soft-skinned mites the colouring appears in most cases to be due to 

 the contents of the body, w^hich when dissolved out, leaves the skin 

 quite colourless and transparent. 



The water-mites are the most beautifully coloured of all the 

 Acarina. The lower forms are usually red, the higher forms 

 exhibiting all the colours of the pallet. This is most noticeable 

 with species of the genus Arrheniiiua. The eyes of one or two 

 genera are on the median line on the anterior portions of the dorsal 

 surface ; but in the majority of the genera the eyes are near the 

 margins of the body> and some species, not satisfied with the 

 marginal eyes, have a median eye as well. This median eye may 

 be on a well marked chitinous plate, or free on the body skin 

 without a special eye plate. 



The epimeral plates on the ventral surface, to which the legs are 

 attached, show a great variation : they may be in groups of four, 

 three, or one. There is also a distinct difference in the sexes of some 

 species, in the shape and grouping of the epimera 



The adults, like spiders, have eight legs. But in the larval 

 stage they have six only. In a number of the adults the legs are 

 well provided with swimming hairs, particularly on the third and 

 fourth pairs of legs. What we call the" crawlers," mites that crawl 

 about on the mud at the bottom of the water and on the stems and 

 roots of aquatic plants have legs which are usually only furnished 

 with short hairs or bristles. 



The genital area also shows great variety in structure. The 

 greater number of species are furnished with chitinous plates on 

 each side of the genital opening on which are placed small discs, known 

 as "acetabula," which vary in number from three to more than 

 fifty on each plate. In the lower forms there is very little difl'erence 

 in the genital area of the sex, but in the higher forms they are usually 

 very distinct. These plates assume different shapes, the most 

 common being lunate or tongue-shaped. Some again have plates 

 in the form of flaps which cover or partly hide the acetal)ula. A 

 few are without plates and have the discs free on the body skin. 

 Between the first pair of epimera is a shield-like plate called the 

 "capitulum." This part contains the mouth organs and the palps are 

 attached to it. The capitulum varies much in shape, usually 

 projecting into a snout which in some species is rather pronounced. 

 The posterior margin usually shows an anchoral process, which 



