402 M. Victor Faussek on the Anatomy and 



and sometimes larger, are found between them. At the 

 periphery of the yolk, where the splanchnic layer of the 

 mesoderm adjoins it, there appears (even before its division 

 into the future hepatic sacs) a number of small cells with 

 small round nuclei; these cells, which in all probability split 

 off from the large endoderm cells, settle down upon the 

 visceral layer of the mesoderm and form the epithelium of 

 the mesenteron. Thus it is not the endoderm cells themselves 

 but their derivatives which give rise to the epithelium of the 

 mid-gut (figs. 31 and 32). 



9. The coxal glands of an adult harvest-man consist of 

 three divisions : — (1) the inner end is expanded in the form 

 of a sac, and constitutes the terminal vesicle ; (2) the terminal 

 vesicle narrows and passes into a very long convoluted tube, 

 the tube of the coxal gland, which has long been known 

 (Malj)ighian vessel) ; (3) the tube empties itself into a large 

 thin-walled sac (urinary bladder), wliich opens to the exte- 

 rior at the side in the cephalothorax, between the cox£e of the 

 third and fourth pairs of legs. The terminal vesicle of the 

 coxal gland has hitherto never been described. It is situated 

 in the cephalothorax as an elongated saccule, at the side of 

 the ganglionic mass sm*rounding the oesoi)hagus, at the base 

 of the third })air of legs ; at the anterior end the saccule 

 bends downwards and somewhat inwards, runs a little way 

 backwards, and terminates blindly near, and on the inside of, 

 the external opening of the coxal gland (fig. 50, es'). In 

 transverse sections we therefore see two lumina, one above 

 the other (fig. 23, <?s^, es^) \ but on scrutinizing a series of 

 sections we can easily convince ourselves tiiat both lumina 

 pass into one another anteriorly, while posteriorly the lower 

 saccule (the doubled-down anterior end of tiie terminal 

 vesicle) ends blindly and the upper one becomes narrower 

 and passes into the tube (fig. 50, es^, es*, cox^ ; tig. 34, es'- ; 

 fig. 35, cox"^). This tube, at first excessively thin (figs. 50 

 and 35, co.t-"), becomes gradually wider, and passes into the 

 long-known convoluted tube, the " Malpighian vessel " of 

 riateau, the true significance of which was first recoo-nizod 

 by Loman *. The tube of the coxal gland forms a conn)li- 

 cated coil, passes towards the dorsal side of the body, where 

 it makes a loop running parallel with the heart, then returns 



• Plateau, '' Sur les phenonienes de la difrestion, etc. cbez les Pbnlan- 

 trides," liull. Acad. Belg. 1870; Rossler, " lieitiiijre zur Aimtomie dor 

 I'lialaiigidi'ii," Zeitschr. f. -wiss. Zool. I5d. 34, 18^2 ; Loruan, " Altes uiid 

 Niiu's ubir das Nejihiidium (die (Aixaldriise) dor Arachnidou," Uijdr. tut 

 do Dioikdo. N. A. .M. 1-J Autl., 1^88. The rocoiit papor by ."^turary 

 (*' Die Coxaldriison dor Aracbnoiden," Arcb. Zool. Instil. Wioii, J> 15d., 

 1891) came iuto luy bands after uiy moiuoir was quite linisbod. 



