ACAEUS SCABIEI. 35 



consists of four more or less distinct joints, on tlie foremost of 

 which there is a hollow, moveable staff, permeated by a sinew, 

 with a sucking cup also perforated in the centre, which is extended 

 flat at the moment of adhesion, and collapses longitudinally, 

 when the animal lets go its hold. At the same time there are 

 some hairs upon the foot which become strong bristles quite 

 anteriorly at the origin of the staff, on the inside of which a 

 sort of short, sharp claw shows itself. The hinder feet are shorter 

 and weaker, and at the same time less clothed with hairs on the 

 side. Instead of the staves with their sucking discs, they have a 

 long bristle, the third pair a longer one than the fourth, and on 

 the inside of this bristle a much smaller bristle or claw. At the 

 base of all the feet there is a powerful, readily recognisable, 

 transversely striated muscular structure. 



The head, which is to a certain extent retractile, consists of 

 two valvular upper-lips, which are firmly coalescent with the 

 slightly toothed jaws ; of two jointed maxilla, which are arranged 

 in the manner of a grating, and saw in a horizontal direction 

 upwards and downwards ; and of the more massive, immoveable 

 lower-lips, which are coalescent beneath, and stand out from each 

 other in the form of a channel above. It has eight fine, inar- 

 ticulate filaments or hairs (four lateral and four directed forwards), 

 arid on each side a vesicular, globular dilatation, which, according 

 to Gudden, probably produces an acrid secretion, which causes the 

 formation of eruptions. The eyes are wanting. After the head 

 follows the oesophagus, with the muscles of the jaws originating 

 from it, and after this a lobate stomach, which is seen most dis- 

 tinctly when it is full of blood, or when the animal is made to 

 swallow oil (for which I regard coloured oils, as, for instance, 

 Macassar oil, as the best adapted), and from the lowest angle of 

 which originates the extremely delicate and slightly curved 

 intestine, which can only be traced in parts when in the full 

 state. The latter opens into the anus, that is, into a longitudinal 

 cleft at the posterior margin of the animal, between the larger 

 orifices of the vagina, through which mature eggs may be passed 

 out by a gentle pressure. Tracheae are wanting. If the mite 

 be laid upon its back and covered with a thin glass, we may, 

 according to Gudden, simultaneously with a movement of the 

 jaws, see air enter in small vesicles into a narrow air -sac, which 

 extends below the oesophagus and stomach, beyond the middle of 

 the ventral surface. But whether this is actually the way in 



