88 Dr. A. Krohn on the presence of two Glandular Sacs 
ring, often of a blackish colour; it leads into a roundish sac, 
often wrinkled in folds, situated in the cephalothorax, and 
communicating with the orifice by a short, narrow canal or 
neck. In many species (Cerastoma cornutum, Phalangium pa- 
rietinum) the two sacs immediately attract the eye, after the 
careful removal of the dorsal shield, by their dark tile-red or 
dark-brown colour, whilst in other’ species (Opilio hystrix, 
Leiobunum rotundum) they appear quite destitute of pigment, 
and are therefore at first easily overlooked*. 
The two sacs, already noticed by that very meritorious ob- 
server Treviranus, but erroneously foarte by him as two 
lateral eyes, prove, upon closer examination, to be glands, the 
intimate structure of which resembles that of many glands of 
Insects. In the first place we may distinguish a very delicate 
outer envelope or tunica propria, immeshed in tracheal rami- 
fications ; this is followed by an epithelium composed of secre- 
tory cells, which is lined by a very transparent cuticle or ¢n- 
t’ma, bounding the cavity of the sac and thrown into numerous 
fine folds. ‘This intima is continuous with the integument at 
the exterior orifice, and consequently proves to be a greatly 
attenuated inversion of the latter into the sac. 
The secretory cells lie close together in a single layer, and 
contain, besides a turbid, finely granular substance, a roundish 
nucleus, and in the vicinity of this a vacuoliform ae which 
usually exceeds the nucleus more or less in size. ach cell 
appears to be connected with the intima by an extremely fine 
efferent canal. ‘The presence of these little canals may be 
easily demonstrated by the action of a weak solution of potash 
upon the sac, by which the cells and pigment are indeed dis- 
solved, but the canals and the folded intima are thereby only 
brought more distinctly into view. The layer of cells may 
be most distinctly perceived in Letobunum. 
In Cerastoma cornutum and Phalangium parietinum, in 
which the sacs, as already stated, are of a dark tile-red or 
brown colour, the pigment, consisting of very minute granules, 
is situated between the cellular layer and the intima, but 
seems, at least partially, to insert itself between the cells. In 
these cases the cellular layer extends to the neck of the sac, 
and the excretory panalicnte are much longer than in Letobu- 
num rotundum and Opilio hystrix; at the same time they are 
strongly coiled together, somewhat in the same way as the 
blood-vessel in the glomerules of the kidneys of Vertebrata. 
Opilio hystrix, the pate of the indigenous species in our 
* In Opilio hystrix only the neck of the sacs shows a blackish or reddish- 
brown tinge. 
