the Endosternite of Scorpio. 25 



and the Eurypterulaj on the one liand and Apvs on the othiT 

 I have already ehiborated in the book above cited, the main 

 conclusion of which I am in a position greatly to strengthen 

 by new points which have lately come to light. The position 

 ot" Scorpio among the Arachnids will be further discussed in 

 a work on Galeodes on which I am now engaged. 



EXPLANATION OF PLATE HI. 



Fiy. 1. The endosternite (shaded) of Galeodes, shown in situ, I, labrum ; 

 p, pedipalp : I., II., III., IV., four pairs of legs ; T, stigmatic 

 opening of trachea ; d, diaphragm, sloping backwards ; h, a, n, t, 

 cardiac, alimentary, neural, and tracheal apertures in d. 

 Fi*/. 2. Transverse sections of the endosternite of Galeodes, showing its 

 nature as two infoldings of the cuticle, joined by staining proto- 

 pla.snnc matter, but not fused, in the middle line, a, alimentary 

 canal ; m, massive elevator muscles of the pedipalps ; s, space 

 filled with staining protoplasmic matter. 

 Fiff. 3. Dorsal aspect of the endosternite of Mi/f/ale. 

 Fifj. 4. Inner view of the ventral surface of Mi/f/cde, showing the ventral 

 points of attachment (1, 2, 3, 4) oi" the endosternite to the 

 stenium (S). ;j, pedipalp; I., II., III., IV., four pairs of legs. 

 Fi(j. 6. Ventral aspect of the endosternite of Mygale, showing its sternal 

 attachments uppermost. From a comparison of these figures 

 the endosternite is seen to be composed of four pairs of apo- 

 demes (1, 1, 1), (2, 2, 2), (3, 3, 3), (4, 4, 4), radiating from a 

 common centre, and further joined by a web-like expansion in 

 the middle horizontal plane. 

 Fig. 6. Dorsal aspect of the endosternite of Phrymis. The preparation 

 was accidentally destroyed before the drawing was completed ; 

 it, however, represents its general appearance. 1,2, 3, 4, ten- 

 dinous attachments, probably corresponding with the first 

 ventral and four dorsal attachments of the endosternite in 

 Mygale. 

 Fig. 7. Dorsal aspect of endosternite of Thelyphonus, after Tarnani (cf. 



last figm-e). 

 Fig. 8. Endosternite (shaded) of Scorpio {Palamncpus Thorellii, Pocoek), 

 in situ. I, labrum ; p, pedipalps ; I., II., III., IV., legs; b, brain, 

 with nerves to p and I. ; d, diaphragm, with h and a, cardiac 

 and alimentary apertures through it, and r, ridges produced in 

 it by the first pair of abdominal dorso-ventral muscles. The 

 diaphragm is seen to slope forward under the endosternite. 

 Fig. 9. Transverse section through the line * in fig. 11, showino- 

 the points of fusion of the endosternite of Scorpio, with the 

 diaphragm, d. g, genital operculum ; I, anterior ends of the 

 lips of the genital aperture. The diaphragm separating the 

 sixth from the seventh segment has here been thrust for- 

 ward by the genital aperture belonging to the seventh segment. 

 e, posterior ends of the endosternite, on one side fused with d, 

 on the other just before fusing, the section not being accu- 

 rately transverse, t, tendons for attachment of muscle-bands, 

 which slope backwards along the anterior face of the diaphrasm 

 (dorso-ventral muscles) ; a, alimentary canal ; n, nerve-cords. 

 Fig. 10. Diagram showing the relative positions of the endosternite and 



