ON DEMODEX PH\LI,OIDES. 279 



work, which projects on the terminal joints into three inwardly- 

 directed hooks. 



The mandibles are 0.04 mm. in length, and in form resemble a 

 pair of shears with rounded points, (md, Fig. 11). 



The oesophagus is short, leading directly into the stomach, which 

 occupies the whole of the thoracic cavity, and is possessed of rudi- 

 mentary caeca answering in position to the appendages, which give 

 the stomach a wavy contour when seen from the side. (Fig. 9). 

 The anus is close behind the sternum. 



In accordance with the views of Leydig, the refractive corpuscles, 

 which are to be seen towards the posterior end of the body in the 

 adults as well as in all stages of development, are regarded as urinary 

 concretions. 



A rudimentary tracheal system is present, which is represented in 

 Fig. 10. No stigmata have been made out. Between the longi- 

 tudinal tracheae are two reniform bodies which Csokor is inclined to 

 regard as central organs of circulation. 



Csokor studied the locomotion of the Demodex in oil on a hot 

 stage. He found that the movements of the mites became very 

 lively with increased temperature, and is inclined to attribute non- 

 success in experiments as to transference to the absence of a suitable 

 temperature for encouraging locomotion. Pedipalpi, head and legs 

 are all active in locomotion ; the head is capable of lateral as well as 

 vertical movement ; at a high temperature, also the abdomen may 

 move upon the thorax so as to form an angle with it. The legs are 

 3-jointed, (Coxa, Tibia and Tarsus; see Fig. 11), but only the two 

 latter take part in locomotion, the tarsus being capable of invagina- 

 tion into the cavity of the tibia. Each tarsus terminates in five 

 equally long claws. 



One of the most important of Csokor's results is the establishment 

 of three ecdyses or moults which take place (I) between the egg 

 and the six-footed larva (Fig. 2) ; (2) between the six and eight- 

 footed larva ; and (3) between the latter and the adult. 



4.— Occurrence and Mode of Life. 



Under this heading Csokor mentions that in the smallest tubercles 



50 — 60 mites may be reckoned, in the larger 500 — 1,000. The 



cast-off cuticles are found towards the centre of the tubercle, the 



younger stages towards the duct of the gland, and the adults 



