ARACHNIDS. 561 



iften rapidly mortal upon those insects on which spiders feed, and 

 iven large flies die quickly when they have been wounded on a 

 jingle foot alone by the bite of Clubiona air ox 1 . 



We have seen that in the spiders, 'from the dilatation of the 

 ntestinal canal situated in the abdomen, which might be taken for 

 he hindmost stomach, large canals proceed to the adipose body. 

 Similarly in the scorpions from the intestinal canal, at nearly equal 

 d very large distances from each other, there arise on each side 

 ve transverse branches which subdivide into finer branches and 

 on through the granular adipose mass. Already, when treating of 



Class of Insects, we directed attention to the suggestion that 

 icre perhaps the adipose body assumed the place of the liver 

 3. 257). In most arachnids (Scorpio, Aranea L.) this part cer- 

 ainly, with still stronger claim, deserves to be thus considered 2 , 

 t consists of lobes, formed of small blind vesicles united in clusters, 

 nd filled with cells. The ducts in question, which run towards 



intestinal canal or proceed from it as branching eversions, are 

 be considered then as gall-ducts. In other arachnids (Phalan- 

 ita, Acarina, Arctisca and Pycnogonida) the glandular walls of the 

 lind intestinal appendages probably serve for the secretion of bile 3 . 



In most arachnids there exist also thin tubes with blind ex- 

 remities which correspond to the Malpighian vessels of insects (see 

 bove, pp. 255, 256), and so are to be considered as subservient to 



urinary secretion. They differ, however, from the vessels of 

 isects alluded to, inasmuch as they usually divide into many 

 ranches. 



The organs for respiration and the circulation of blood are not 

 i these animals formed after one and the same type. When 

 aspiration is performed by means of air-tubes, there is a dorsal 

 ssel, as in insects, a longitudinal heart, without branches ; vessels, 

 Li the other hand, are found in those genera in which the respira- 

 >ry organs are sacciform lungs, and are not spread throughout the 

 ody as air-tubes. In Phalangium, the heart is a dorsal vessel 

 'ithout branches, which becomes narrower at both extremities, 

 id is divided by constrictions into three chambers, or dilata- 



1 TREVIRANUS, Ueber d. inn. Sau d, Arachn. s. 31, 32, Tab. 2, figs. ii t 22. 

 8 J. F. MECKEL Beytrage z. vergl. Anat. T, 2. 1809. s. 108. See also especially 

 [ASMANN 1. c. pp. 145 148, Tab. 13, figs. 20 22. 

 3 V. SIEBOLD, Lehrb. der vergl. Anat. I. s. 529. 



VOL. I. 36 



