COMPARATIVE MORPHOLOGY OF THE GALEODID^. 335 



Tendons. — The development of long tendons for the movement of the limbs is especially noteworthy in 

 Arachnids. Galeodes is no exception in this respect. These tendons appear in some cases to be 

 closed cuticular invaginations. They can often be seen to be hollow. They further attract the small 

 pigment-bodies already alluded to. The long distal tendons may be adaptations in the interest of strength, 

 by permitting the muscle-masses to be situated in the larger proximal joints, where they can develop to 

 greater size than would be possible in the smaller distal joints. The short tendons on the proximal 

 joints specialize the actions of the muscles in accordance with the highly developed locomotory powers 

 of so many of the Arachnids. 



V. The Mtjsculae, System. 



The division of the body into two specialized regions, the anterior for locomotion, the 

 posterior for digestion and reproduction, has naturally led to great modification in the 

 dermo-muscular tube, which may be assumed to have been the primitive arrangement in 

 all articulate animals. Nevertheless, we can still refer many of the muscles of Galeodes 

 to the elements of a typical Annelidan musculature. We have, for instance, both 

 circular dermal muscles and longitudinal dermal muscles and a series of segmentally- 

 arranijed dorso-ventral muscles. 



The Muscles of the Body : the Circtilar Musculature. — In the cephalothorax, the muscles 

 which most obviously belong under this heading are the skin-muscles at the sides of the 

 body, where the cuticle is soft and flexible, just above the bases of the anterior limbs, at 

 the sides beneath the so-called " head " (PI. XXVII. fig. 2). The distal end of the coxal 

 gland passes among these muscles, and is then very diflicult to follow. These muscles 

 probably bring about a certain amount of movement of the " head.'' 



As might be expected, it is in the abdomen, where the cylindrical segments are least 

 •diflferentiated, that the circular muscles are retained over considerable areas. The lateral 

 flexible membrane on each side of the body is lined by a layer of circular fibres. 

 Anteriorly, these fibres form only a single layer; postei'iorly, however, the layers gradually 

 thicken. The increase in the development of the circular muscles towards the posterior 

 end of the abdomen is correlated with a corresponding diminvition in development in 

 the longitudinal muscles (cf. PL XXX. figs. 11, 15). These abdominal circular fibres 

 show at times only a longitudinal striation, at others a transverse striation also ; 

 they are capable of enormous extension when the abdomen is distended after a 

 meal. 



These circular muscles are found under the flexible lateral membranes in Scorpio and the Pedipalpi, 

 and both in the cephalothorax and abdomen of the Pseudoscorpions. They are also present in the 

 abdomen of Spiders {Li/cosa), where Ihcy seem to be evenly developed under the cuticle. 



The Longitudinal Muscles. — These are also well developed in Galeodes. Dorsally, 

 they rim in two strong bands on each side of the median line from the tergum of 

 the 3rd segment, part of which lies under the posterior end of the cephalic lobes, to the 

 diaphragm, and then along the abdomen, on each side of the heart, gradually diminishing 

 in development towards the stercoral pocket, where the circular muscles correspondingly 



