282 AQUATIC MICROSCOPY FOR BEGINNERS. 



the animal, and deep enough not to injure the soft 

 body, yet shallow enough to restrain its movements. 



The mouth of the mite is usually a complicated 

 affair, and is sometimes surrounded by a circular ele- 

 vation or ring called a hood, and always having short, 

 jointed palpi, or feelers. At some distance back of 

 the mouth, in a few forms, near to the posterior border 

 but always in the median line, will be seen, in the 

 female mites, a small dark spot or narrow line which 

 is really an opening. In some species this orifice, 

 which may be called the ventral opening, is covered 

 and concealed by a large plate, called the ventral plate; 

 or there may be two plates, curved, oval, or other 

 shape, one on each side of the ventral opening. They 

 are useful to the naturalist as one means by which the 

 mites may be classified, and they should be carefully 

 searched for by the observer who desires to learn the 

 name of his specimen. They are not present in the 

 males. The reader will therefore perceive that to 

 identify his captive the specimen must be a female. 

 The two sexes, however, differ so conspicuously in 

 appearance that they are easily recognized. The 

 female always has the posterior border of the body 

 more or less evenly rounded; while the male frequently 

 possesses a peculiar little tail-like process projecting 

 from the middle of the posterior margin. . One form 

 of this curious projection is shown in Fig. 196, a fe- 

 male by Fig. 191, the projection varying in shape and 

 size in the different species. The males seem much 

 less abundant than the females; they are, at least, less 

 frequently captured by the microscopical fisherman. 



On the ventral surface, behind or before, or on both 

 sides of the ventral plates, will be observed one or 



