MANUAL OF ZOOLOGY. 



The mouth is situated, in all the Arachnida, in the anterior 

 segment of the body, and is surrounded by suctorial or mas- 

 ticatory appendages. In the higher Arachnida, the mouth is 



Fig. 161. A, The male of the common House-Spider (Tegenaria ci-vilis), considerably 

 magnified : c Front portion of the body, consisting of the amalgamated head and 

 thorax ; / Maxillary palpi ; a Abdomen. B, Front portion of the head of the same, 

 showing the eight eyes (/}, and the mandibles (). C, Under side of the head and 

 trunk, showing the true jaws (in), the lower lip (/), and the horny plate to which the 

 legs are attached. D, Diagram of one of the air-chambers or breathing-organs. 

 (Figs. A, B, and C are after Blackwall.) 



provided from before backwards with the following appendages 

 (figs. 161, 162): i. A pair of "fakes," or "mandibles," used 

 for prehension ; 2. A pair of " maxillae," each of which is pro- 

 vided with a long jointed appendage, the " maxillary -palp ;" 

 3. A lower lip, or " labium." In the Scorpion, an upper lip, 

 or "labrum," is also present* 



* The nomenclature ordinarily applied to the parts of the mouth in the 

 Arachnida is a misleading one, so far as the homologies of this class with 

 the Insecta are concerned. Thus the so-called "mandibles " are really the 

 antenna ; the "mandibles" themselves are absent, but the "chelae" of the 

 Scorpions may really represent the " mandibular palpi; " whilst the first 

 pair of legs really correspond with the " labial palpi," and the second pair 

 of legs may possibly be a modification of a second pair of palps. 



