412 MK. H. M. BERNARD ON THE 



Fig. 10. Diagram illustrating some of the muscles of the eudosternite ; ep, elevator of the pedipalps; 

 p, fibrous plate; e, eudosternite (c/. PI. XXVIII. lig. 16 and text, p. 339). 



11. Interual aspect of ventral abdominal surface of Galeodes arabs. On the left, the aiTangement 



of the ventral longitudinal muscle-bands [vim], on the right the ovary (?) {ov). Anteriorly 

 is the diaphragm (D) ; h, aperture for the heart ; in, for the intestine. The other apertures 

 in the diaphragm are for tracheae (c/. figs. 13 aud 14) ; the median nerve swells into a 

 ganglion {abg) ; the lateral nerves (h) belong to the genital gland. 



12. Muscle-fibres iu section, each fibre surrounded by a fine connective-tissue sheath. 



13. Lateral view of the main tracheal trunks of the left side, the pericardial trachea [pet) being 



median. 



14. View of the abdominal tracheal system, with the exception of the pericardial trachea, which, 



however, has 8 points of connection [pet'), viz. from a pair of branches iu the 1st segment, 

 and from a single brauch on the right side iu the 2ud segment. The ventral ends of the 

 dorso-ventral muscles [dv) attached in the median line are shown cut through. On the right, 

 part of the maiu tracheal trunk is omitted in order to show the tracheae supplying the cuticle 

 and the ventral longitudinal and lateral muscles. 



15. Pericardial trachea [pet), aerating the heart {h) ; the dorsal longitudinal [dim) and the circular 



(lateral) muscles (hn). For the origins of this system, see figs. 13 and 14 {pet'). 



16. Part of a transverse section through a pair of abdominal stigmata, m, the median fold of skin 



to which, anteriorly to the stigmata [cf. fig. 14), the dorso-ventral muscle is attached. 

 Small muscle-bands on each side appear to dilate the stigmatic apertures [stiff). The stig- 

 matic combs {co) appear, in situ, cut through iu the section. 

 17 « & 17 6. Two figures explaining the histology of the tracheal tubes, ff, the glassy layer of the 

 cuticle continued as the lining of the tube, under which occurs the staining chitinogenous 

 layers (ch), which is greatly thickened to form the spiral hoops {cf. fig. 17 i, with PI. XXXI. 

 hg. 7, which shows the thickening of the laminae of the chitinogenous layers to form the lens 

 of the eye) ; ep, epithelium ; n, nuclei of epithelial cells. 



18. Longitudinal section through a cephalothoracic stigma of a Rhax. The sette modified to 



form a protective sieve. The flat-headed hairs within the aperture appear to be open at 

 their tips, and may be olfactory. 



19. An abdominal stigma of the same animal appearing in a sagittal section. It is seen well pro- 



tected by the stigmatic fold. Digestive tubules [dt) are seen penetrating into the fold. 



Plate XXXI. 



Fig. 1. Nearly median longitudinal section through Rhax. ot, optic tubercle; dm, divaricator 

 of the left chelicera cut through ; ^3, apodeme formed by the posterior portion of the 

 cephalic lobes resting on the 3rd tergite ; niff, outline of mid-gut ; ce, oesophagus ; 

 en, central nerve-mass ; b, buttress round which the left pedipalp rotates ; eg, convolutions 

 of the main ducts of the coxal glands; e, eudosternite; D, diaphragm ; h, heart ; /r, tracheal 

 tube. 



2. Sagittal section through the central nerve-mass (the hue details of which can only be dia- 



grammatically suggested), showing the relative jjosition of the principal ganglionic centres. 

 on, optic nerve ; ch, nerve to the chelicera ; pp, ditto to the pedipalp ; 1, 2, 3, 4, ganglia of 

 the 1st, 2nd, 3rd, and 4th legs ; ce, oesophagus. 



3. Showmg the relative positions of the same ganglionic centres iu different Arachnids. 



a. Spider, showing least specialization (i. e. forward and upward tilting) ; b, Gultodes ; 

 c, Scorpio ; d, outline of central nerve-mass of Phalanyium ; e, relative positions of ganglionic 



