278 on demodex phylloides. 



The Skin. 



In the abdominal region the cuticle is transversely striated, an 

 appearance which Csokor attributes to segmentation. In the head 

 the cuticle is not so closely applied to the underlying parts as in the 

 rest of the body — a clear margin resulting, to which Megnin has 

 applied the term epistome. In the thoracic region the cuticle is 

 locally thickened along certain lidges which thus form a chitinous 

 framework. The mesial element of this is the sternum, which gives 

 off laterally four pairs of epimera, and projects also beyond the 

 origin of the last pair of epimera almost as far as the anus. The 

 first pair of epimera run obliquely forwards and form the boundary 

 between the head and thorax. The basal joints of the four pairs of 

 appendages are movably articulated to the outer thirds of the 

 corresponding epimera. 



The appendages of the head are three pairs, viz. : 1 pair of 

 mandibles, 1 pair of maxillae, 1 pair of pedipalpi, and an impair 

 stylet-like structure between the maxillae (Ig, Fig. 11\ which, 

 together with these, forms a piercing apparatus, while the mandibles 

 and pedipalpi move chiefly from side to side, and are therefore 

 masticatory. All of these appendages are attached to the cephalic 

 segment, (cp, Fig. 11). On the cephalic segment are also to be 

 noticed two punctiform ocelli (oc, Fig. 11), and close beside the 

 contour of the pharynx (ph, Fig. 11) are two openings (dc, Fig. 11) 

 apparently belonging to glands in connection with the pharynx. 



The development of the cephalic segment and its appendages is 

 illustrated in Fig. 1-5. First a retraction of the granular contents 

 is noticeable (Fig 1 ), then a demarcation of the hyaline region as 

 head (Fig. 2), in which an anterior notch containing a pyramidal 

 outgrowth is bounded by two lateral curved processes ; these are 

 the future pedipalpi, while the pyramids by a division in the middle 

 line (Fig. 3), and the subsequent longitudinal division of each half 

 gives rise laterally to the mandibles, medially to the maxillae 

 (Fig. 4-5). 



The maxillae are curved rods 0.01 mm. in length, (mx, Fig. 11). 

 Although chiefly piercing organs, they can also be moved from side 

 to side. 



The pedipalpi are three- jointed, the middle joint being soft, while 

 the basal and terminal joints are provided with a chitinous frame- 



