§> 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 sj'stem 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 exti-emities.*^* 



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. Beneden has observed, in the extremities of these 



13, 15 ; this author has seen four pairs of hepatic animals, regular blood-currents produced appar- 



ducts. See, also, Treviranus, Bau d. Arachn. p. 8, ently by contractile membranes at the base of the 



Taf. I. fig. 6, A. v., and Blixller, loc. cit. p. 35, 46, legs ; see Institut. No. 627, or Froriep''s neue 



Taf. II. fig. 22, D. D.; finally Newport, Philosoph. Notiz. XXXVII. p. 72. 



Trans. 1843, PI. XIV. flg. 32. ^ For the blood of the Arachnoidae, see Wafrner^ 



1 C. Ä. S. Schnitze (in his memoir "Macro- Zur vergleich. Physiol, d. Blutes, Heft. I. p. 27, fig. 



biotus llufelandii ") thinks he has observed blood- 11 {Scorpio evropaeus) ; Horn, Das Leben des 



vessels in the Tardigrada ; but neither Doyire Blutes, p. 10, Taf. I. fig. 12 {Tegenaria dnmes- 



(loc. cit. p. 310) nor I have been able to lind tica), and Doyire, loc. cit. p. 309, PI. XV. fig. 5. 



them. For the interstitial circulation of tlie Pycno- {Tardigrada.) 

 gonldae, see Quatrefages, loc. cit. p. 76. Fan 



* [ § 308, end.] See, for some researches upon thereby of the nature of the alleged hepatic append- 

 the hepatic organs of the Arachnoidae by means of ages of the alimentary canal of these animals» 

 chemical agents, and the positive determination Will, Müner''s Arch. 1848, p. 50'. — E». 



