ARACHNIDS. 561 
often rapidly mortal upon those insects on which spiders feed, and 
even large flies die quickly when they have been wounded on a 
single foot alone by the bite of Clubiona atrox?. 
We have seen that in the spiders, from the dilatation of the 
intestinal canal situated in the abdomen, which might be taken for 
the hindmost stomach, large canals proceed to the adipose body. 
Similarly in the scorpions from the intestinal canal, at nearly equal 
and very large distances from each other, there arise on each side 
five transverse branches which subdivide into finer branches and 
run through the granular adipose mass. Already, when treating of 
the Class of Insects, we directed attention to the suggestion that 
there perhaps the adipose body assumed the place of the liver 
(p.-257). In most arachnids (Scorpio, Aranea L.) this part cer- 
tainly, with still stronger claim, deserves to be thus considered?. 
It consists of lobes, formed of small blind vesicles united in clusters, 
and filled with cells. The ducts in question, which run towards 
the intestinal canal or proceed from it as branching eversions, are 
to be considered then as gall-ducts. In other arachnids (Phalan- 
gita, Acarina, Arctisca and Pycnogonida) the glandular walls of the 
blind intestinal appendages probably serve for the secretion of bile®. 
In most arachnids there exist also thin tubes with blind ex- 
tremities which correspond to the Malpighian vessels of insects (see 
above, pp. 255, 256), and so are to be considered as subservient to 
the urinary secretion. They differ, however, from the vessels of 
insects alluded to, inasmuch as they usually divide into many 
branches. 
The organs for respiration and the circulation of blood are not 
in these animals formed after one and the same type. When 
respiration is performed by means of air-tubes, there is a dorsal 
vessel, as in insects, a longitudinal heart, without branches; vessels, 
on the other hand, are found in those genera in which the respira- 
tory organs are sacciform lungs, and are not spread throughout the 
body as air-tubes. In Phalangiwm, the heart is a dorsal vessel 
without branches, which becomes narrower at both extremities, 
and is divided by constrictions into three chambers, or dilata- 
1 TREVIRANUS, Veber d. inn. Bau d. Arachn. s. 31, 32, Tab. 2, figs, 21, 22. 
* J. F. Mecken Beytrige z. vergl. Anat. 1, 2. 1809. s. 108. See also especially 
WASMANN I. c. pp. 145—148, Tab. 13, figs. 20—22. 
3 V. Sresoxp, Lehrb. der vergl. Anat. 1. 8. 529. 
WON. 1. 36 
