WATER MITES 43 



Behind these the body contracts slightly from side to side, 

 passing thence into a sweeping curve extending round the 

 posterior end of body. The skin is covered with small, 

 rounded papillae, and along the dorsum are four rows of 

 gland pores, each with its guard hair. It will be observed 

 that the pores of the two inner rows are connected longi- 

 tudinally and transversely by a weak depression, suggesting 

 the outline of a ladder. In some respects, young forms differ 

 somewhat from the older, the outline being more oval and 

 the dorsum slightly arched. On the anterior dorsum will be 

 noticed two eye capsules, lying on the flattened portion of the 

 anterior edge of body. Each capsule consists of two portions, 

 a large anterior and a small posterior one, each containing 

 an eye of corresponding size. On the median line, a little 

 posterior to these, is the so-called median eye, surrounded by 

 a small chitinous ring. In some species the ring develops 

 into a well-marked plate. Between the eyes, on the body 

 margin, are two short bristles these are known as the 

 antenniform bristles. The dorsum does not here call for 

 further comment ; more detail is, however, presented by the 

 venter. As indicated before, there are eight epimeral plates, 

 four on each side, fused into two groups the first pair to the 

 second, and the third to the fourth. The first pair are long 

 and narrow, and of about equal width throughout. The 

 second pair are shorter and rather broader, their posterior 

 end being somewhat acute. The fourth pair are rather more 

 rectangular than the third. The interval between the groups 

 is considerable, and the edges are thick, with a number of 

 hairs dotted along them. The capitulum is situated between 

 the first pair of epimera, to a limited degree it is capable 

 of being protruded or retracted. The capitulum is cone- 

 shaped, with the apex bent rather towards the ventral surface. 

 At the apex is the mouth, with its finely ridged edge and 

 four hairs slanting round. The palpi are articulated laterally to 

 the capitulum. The first segment is short, the second and 

 third have numerous short pectinated bristles, the fourth 

 is much longer and slender, and ends in a conical process. 

 The fifth segment is very short and peg-like, and articulates 

 with the fourth so as to form a kind of pincer. 



