^309. 



THE ARACHNOIDAE. 



381 



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 VI 



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. vn. fij. 

 13, 15 ; this author has seen four pairs of hepatic 

 ducts. See, also, Treviranus, Bau d. Arachn. p. 8, 

 Taf. I. fig. 6, A. v., and Miiller, loc. cit. p. 35, 46, 

 Taf. II. fig. 22, D. J>. ; finally Newport, Philosoph. 

 Trans. 1843, PI. XIV. fig. 32. 



1 C. A. S. Schultze (in his memoir " Macro- 

 biotus Hufelandii ") thinks he has observed blood- 

 vessels in the Tardigrada ; but neither Doyire 

 (loc. cit. p. 310) nor I have been able to find 

 them. For the interstitial circulation of the Pycno- 

 gonidae, see ^uatrefages, loc. cit. p. 76. Van 



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, Ileft. I. p. 27, fig. 

 11 {Scorpio evropaeiis) ; Horn, Das Leben des 

 Blutes, p. 10, Taf. I. fig. 12 (Tegenaria domes- 

 tica), and Doyire, loc. cit. p. 309, PI. XV. fig. 5 

 (Tardigrada^ 



* [ § 308, end.] See, for some researches upon 

 the hepatic organs of the Arachnoidae by means of 

 chemical agents, and the positive determination 



thereby of the nature of the alleged hepatic append- 

 ages of the alimentary canal of these animals. 

 Will, Mailer's Arch. 1848, p. 507. —Ei>. 



