410 ME. H. M. BERNAED ON THE 



Fi^. 16. Side view of the endosternite, fibrous plate {p), the supporting rod (chj-), and the eoxal 

 gland (cff). e, point of origin of rigiit half of the endosternite. 



17. From a section through e (fig. 16), showing the endosternite as an infolding of the cuticle. 



18. Transverse section through the endosternite, showing the interlocking of the right and left 



halves [e^, C;) in the middle line and the ftision with the supporting rod {chr) [cf. figs. 15, 

 16). The fibrous tissue (ft), binding the portions together, stains deeply. The nature of 

 the endosternite as a chitiuous infolding is apparent (cf. fig. 17). 



19. Longitudinal section through the fibrous plate (p). 



Plate XXIX. 



Fig. 1. Diagrams to suggest an origin for the two types of Arachnidan cheliceras from an original 

 3-jointed limb, a, b, c, is the order of development for the type found in the Spiders 

 and Pedipalpi. a, b' , the same for that of Scorpio, Phalangids, and Pseudoscorpions. a, b' , c' , 

 for Galeodes, Gamasus, and other Acari. In c , str represents the position of the stridu- 

 lating apparatus found in certain Galeodidse {cf. text, p. 322). 1, 2, 3, the three joints and 

 their modifications, o, ocular tubercle, cl, cephalic lobe. 

 2 (twisted round by mistake). Section through the tip of a cheliccra of P//?'yMi<,s, showing what 

 may be a trace of a lost joint, 7. fc, flexible chitin ; set, setae, ? homologous with the spinning- 

 glands of Pseudoscorpions, and poison-glands of Spiders, opening in practically the same spot. 



3. Side aspect of the anterior end of a small Galeodes, showing the relative sizes and positions 



of the pedipalps (^pp) and 1st pair of legs, also the enormously long sensory hairs, only a 

 very few of which are drawn, ol, joint containing the olfactory organ at the tip of the 

 pedipalps [cf PI. XXXI. figs. 10-17). 



4. The same of a Rhax, showing the relative sizes and position of the same limbs. The terminal 



joints of the pedipalps {ol) are immovable, le, lateral eyes. 



5. Hypothetical diagram, showing the character and position of the three first limbs in the 



primitive form [cf. fig. 14) . 



6. Ventral aspect of Rlia.v to show the sequence between the coste of the cephalo thoracic limbs 



and the paired ventral plates of the abdominal segments. 



7. To show the continuity between the genital operculum [go] of a Galeodes and the cephalo- 



thoracic limbs ; the chitinous folds {cf) of the former continue the interarticular folds 

 (between coxa and trochanter) of the cephalothoracic limbs (cf. fig. 11). 



8. Ventral abdominal surface of a Galeodes intrepidus, Savigny, in the British Museum (abdomen 



not distended), showing the ventral plates (limb-areas), continuing the plates forming the 

 genital opercula. 



9. The same of a specimen of G. fat alls (abdomen somewhat distended), showing the sequence of 



the paired plates (/a). 



10. The ventral median line of a Galeodes (?sp.), also in the British Museum, showing in more 



detail the characters of the limb-areas, ffo, genital opercula ; stiff. o, stigmatic opercula. 



11, 12, 13. Hypothetical restorations of abdominal limbs to explain the position of the stigmata. 



11. Galeodes. The stigmata on the posterior faces of the coxae (5//^.o = stigmatic opercula) 

 have been brought in towards the middle line by the bending backward of the limbs. 



12. Scorjjio. The limbs retained their lateral positions, but sloped backward. 13. Thely- 

 phonus or Phri/nus. The spinning-glands {r/ff) in the genital limb (go) (" penis " of 

 Phrynus) appear to be homologous with the glands {gy) on the same limbs in Galeodes. 

 eg, aperture of the coxal gland; stig, stigmata, persistent or aborted. 



