Coxal Glands of Scorpio. 59 
often erroneously called the “liver.” The Malpighian tubules 
have here, as it appears to me, become specialized for the 
removal of fecal matter from the tips of the diverticula *. 
In this case the waste products appear to be entirely used up 
in the formation of silk. 
We find, then, a distinct physiological connexion between 
the purely excretory glands and the silk-glands; when the 
latter are well developed, the former tend to atrophy or to 
become specialized for other functions, and, on the other 
hand, when there are no glands for using up the waste products 
the purely excretory glands are well developed. ‘This 
physiological relationship need not necessarily imply any 
homology between the spinning- and poison-glands, on the 
one hand, and the excretory glands (coxal glands and Mal- 
pighian vessels) on the other, At the same time the common 
derivation of all these glands from setiparous sacs would 
render such connexion very natural. 
EXPLANATION OF PLATE IL 
Fig. 1. A transverse section of Huscorpio italicus, passing through the tip 
of the coxa of the fourth leg, c,. ¢3, coxa of third leg, the pos- 
terior face of which is fused with the anterior face of c,, leaving, 
however, an open channel, ch ; en, endosclerite ; ”, nerve to the 
third leg (the accompanying blood-vessel gives off a branch, 6, 
to the coxal gland); sp, sternal plate. 
Fig. 2. A few sections further back, showing the part of the duct (d) 
leaving the chitinous channel (ch), and the blood-vessel (0) 
running backwards. The coil of the coxal gland is also cut 
through tangentially ; nuclei in various stages of vesiculation 
are found, the largest and most vesicular being detached. 
Fig. 3. A portion of the cuticle of Palamneus Thorellit, Pocock, macerated 
in caustic potash, showing the posterior face of the coxa of the 
third leg seen from within. ma, chitinous attachments for 
muscles ; ch, the channel between c, and c,; d, chitinous intima 
close to the aperture of the duct; sp, portion of the sternal 
late. 
Fig. 4. Lean section through the end-saccule (the so-called “ medul- 
lary substance”), The clear portions are the blood-passages, 
the dotted parts are the tubules of the end-saccule. The opening 
of the blood-vessel is marked by a curious aggregation of cells (¢) 
(? Sturany’s “ Blutzellen”) between which the blood flows. 
Fig. 5. Posterior section through the end-saccule, showing that the latter 
is but an expansion of the coiled duct. Between the scattered 
epithelium of the end-saccule and the highly specialized epithe- 
lium of the coiled duct occurs a short band of epithelium appa- 
rently quite undifferentiated. 
Fig. 6. Diagram of the gland, showing the special blood-vessel discharging 
its contents among the tubules of the end-saccule. Lettering as 
above. 
* “Notes on some of the Digestive Processes in Arachnids,” Journ. R, 
Micr. Soe. (in press). 
