$ 309. THE ARACHNOIDAE. 881 
With the Scorpionidae, the liver is also very large, and composed of many 
lobes. It occupies the two sides of the abdominal cavity even to the base 
of the tail, and closely encompasses the intestine, the heart, and the genital 
organs, The ramifications of the biliary canals traverse, in groups, the 
parenchyma of this liver, and the bile is poured into the intestine by five 
pairs of short, excretory ducts, equally, but very widely separated from 
each other.© * 
CHAPTER VIL. 
CIRCULATORY SYSTEM. : 
§ 309. 
With many Arachnoidae, the circulatory system consists only of a Heart 
or an articulated.dorsal vessel. 
With the higher forms, there is, in addi- 
tion, a system of more or less developed blood-vessels; while with the 
lower species, such as the Tardigrada, the Acarina and the Pycnogonidae, 
not only all these vessels, but the heart, also, is absent. There is, there- 
fore, in these last, no regular circulation, but the nutritive fluid fills all the 
interstices of the body, and, by the aid of the muscular movements and the 
contractions of the intestinal canal, is transferred in an irregular manner 
hither and thither in the visceral cavity and in the extremities.” 
The Blood of the Arachnoidae is entirely colorless, and has a slightly 
milky aspect only when in considerable quantities. 
It contains a few 
granular blood-cells of a pretty regular, spheroidal form, and some very 
small, isolated granules, derived perhaps from broken blood-cells. 
8 See Meckel, Beitr. &c. p. 107, Taf. VII. fig. 
18, 15; this author has seen four pairs of hepatic 
ducts. See, also, J'reviranus, Bau d. Arachn. p. 8, 
Taf. I. fig. 6, A. v., and Muller, loc. cit. p. 35, 46, 
Taf. II. fig. 22, D. D.; finally Newport, Philosoph. 
Trans. 1843, Pl. XIV. fig. 32. 
1C. A. §. Schultze (in his memoir ‘ Macro-~ 
biotus Hufelandii ”) thinks he has observed blood- 
vessels in the Tardigrada; but neither Doyere 
(loc. cit. p. 310) nor I have been able to find 
them. For the interstitial circulation of the Pycno- 
gonidae, see Quatrefages, loc. cit. p. 76. Van 
* [§ 308, end.] See, for some researches upon 
the hepatic organs of the Arachnoidae by means of 
‘chemical agents, and the positive determination 
Beneden has observed, in the extremities of these 
animals, regular blood-currents produced appar- 
ently by contractile membranes at the base of the 
legs; see Institut. No, 627, or Froriep’s neue 
Notiz. XXXVII. p. 72. 
2 For the blood of the Arachnoidae, see Wagner, 
Zur vergleich. Physiol. d. Blutes, Heft. I. p. 27, fig. 
11 (Scorpio europaeus); Horn, Das Leben des 
Blutes, p. 10, Taf. I. fig. 12 (Tegenaria domes- 
tica), and Doyere, loc. cit. p. 809, Pl. XV. fig. 5 
(Tardigrada.) 
thereby of the nature of the alleged hepatic append- 
ages of the alimentary canal of these animals, 
Will, Miller’s Arch. 1848, p. 507. — Ep. 
