§ SOT. 



THE ARACIINOIDAE. 



;79 



diverticuli, of the most varied form and size. It is continuous into a short, 

 small intestine, which passes, in a straight line, to the anus situated usually 

 at the posterior extremity of the body. Before reaching this point, the 

 intestine has, usually, a dilatation bounded by a constriction, which may be 

 regarded as a rectum, or better, perhaps, as a cloaca. With the Tardi- 

 grada, the stomach is oblong and occupies a large portion of the body. It 

 is divided throughout by numerous constrictions into many irregularly dis- 

 posed caeca. *^' 



With the Acarina, whose anus is placed nearer the middle of the belly, 

 there are, nearly always, three short caeca at the anterior part of the 

 stomach, and two, longer and more or less constricted, in the lateral regions 

 of the abdomen. With some species of parasitic Mites, these appendages of 

 the stomach are bifurcated.'-' With the Pycnogonidae, the stomach is short, 

 but has five pairs of very long caeca, some of which penetrate into the two 

 cheliceres, and others into the eight long legs, even to the extremity of the 

 tibiae.'^' With Galeodes, also, these appendages penetrate the legs, and 

 the base of the cheliceres and palpi. '^' With the Phalangidae, the stomach 

 is spacious and has thirty appendages of varied size. Thus, at its upper 

 jiart, there are four rows of short caeca, and, upon the sides, three pairs, 

 very long and extending over nearly the whole length of the visceral cavity ; 

 the middle pair of these last has, moreover, short sacculi.*^* With the Araneae, 

 the stomach is situated in the cephalothorox, and presents a very remark- 

 able disposition. At the posterior extremity of the thoracic cavity, and 

 directly behind the sucking apparatus, it is divided into lateral halves 

 which extend arcuately in front, and, uniting, form a ring from which are 

 given off laterally five pairs of caeca extending towards the points of inser- 

 tion of the legs and palpi. 



The intestine arises from this annular stomach, opposite the sucking 

 apparatus. It traverses the abdomen on the median line, and terminates, 

 before I'eaching the anus, in a cloacal dilatation."*' 



2. With the Phrynidae,'*^' and Scorpionidae,® the intestinal canal is 

 very simple compared with that just described. It consists of a straight 



1 Doyire, Ibid. p. 324, PI. XV. 



2 See Lijonet, loc. cit. PI. XIII. fig. 11, 12 ; 

 Dugis, loc. cit. I. PI. I. fig. 27. II. PI. VII. {Erij- 

 thraeus, Dermanyssus and Ixodes) ; also, Tre- 

 viranus, Zeitsch. f. Pliysiol. IV. p. 189, Taf. XVI. 

 Ixodes has dichotomous stomachic appeixlages, of 

 which the posterior, at the extremity of the body, 

 curve first downwards, then forwards with a long 

 course. These various caeca of the Acarina often 

 appear, especially when filled with food, clearly de- 

 fined, through the skin. But when empty, they 

 are frequently overlooked in the small species, 

 from the tenuity of their walls. However, I have 

 always succeeded, even with the smallest Oribatea, 

 in distinguishing the walls of the intestine, especially 

 when it contained food. I must, therefore, consider 

 as wholly erroneous, the opinion recently advanced 

 by Dujardin (Ann. d. Sc. Nat. III. p. 14, or 

 Compt. rend. loc. cit. p. 1159), that the food eaten 

 by the Acarina does not pass through a distinct 

 digestive tube, but is freely effused in the interstices 

 of the viscera. 



3 Milne Edwards, Hist. Nat. d. Crust. III. p. 

 631, and Quatrefages, loc. cit. p. 72, PI. I. II. 



i Blancliard, loc. cit. p. 1384. 



5 Ramdohr, Abhandl. Cib. d. Verdauungswerk. 

 p. 205. Taf. XXIX. ; Treviranus, Verm. Schrift. 

 I. p. 29, Taf. III., and Tulk, loc. cit. p. 246, PI. 

 IV. 



For the annular stomach of the Araneae, and 

 on which, with Tegenaria, Treviranus (Bau d. 

 Arach. p. 30, Taf. 11. tig. 24, v. b.) has found only 

 four caeca, see Brandt, Mediz. Zool. II. p. 89, Taf. 

 XV. fig. 6, or Ann. d. Sc. Nat. .XIII. p. 182, PI. 

 IV. fig. 2, or Isis, 1831, p. 1105, Taf. VII. fig. 6 ; 

 also Owen, Lectures, &c., p. 257, tig. 110; and Was- 

 mann, loc. cit. p. 11, fig. 17, 18. According to 

 this last observer, the four pau's of stomachic caeca, 

 with Mygale, bend downwards to the base of the 

 eight legs, in order to pass into the thorax where 

 they ramify and interanastomose. 



yiiih Argyroneta, audi some species of £pej>a, 

 according to Grube (Miil/er^s Arch. 1842, p. 208), 

 the lateral halves of the stomach are not united in 

 a ring at their anterior extremity, but are only con- 

 tiguous. 



With the Araneae, the walls of the stomach con- 

 tain finely-granular cells which, by rettccted light, 

 have a milky aspect, and secrete perhaps a kind 

 of gastric juice. 



7 Fan der Hoeven, Tijdschr. &c. IX. p. 68 

 {Phrynus). 



8 Meckel, Beitrage, loc. cit. p. 107, Taf. VII. 

 fig. 13 ; Treviranus, Bau d. Arach. p. 6, Taf. I. 

 fig. 6, and Mailer, loc. cit. p. 45, Taf. 11. fig. 

 22. 



