378 ■ THE ARACHXOIDAE. § SOT. 



nal side of, or underneath the basilar article. It is erected when the 

 animal, for defence, or for the seizure of its prey, inflicts a poisonous 

 wound ; and, for this purpose, the excretory drfct of a poison-gland 

 opens at the apex of each of these hooks. *"> The first pair of maxillae is 

 changed, with the Araneae, into very long tactile, and with the Phrynidae» 

 into prehensile organs. Their basilar articles form two upwardly directed 

 prominences, which are contiguous at their bristly, internal borders, and 

 thereby cover the entrance of the oral cavity.'^"* As the Araneae bruise,, 

 by means of these prominences, their prey which they have seized and 

 taken into their mouth, these parts may be regarded as rudimentary 

 maxillae. 



The entrance of the Oral cavity is surrounded, with most Arachnoidae, 

 by a soft, unequal border. This may be regarded, in part, as an upper and 

 under lip, and partly as a tongue.'"' The orifice and cavity of the mouth 

 are often provided with small hairs pointing inwards, among which are 

 sometimes observed horny ridges, which serve, probably, as teeth. The 

 Araneae have this peculiarity, that their large oral cavity has a groove on 

 the median line of the palate, which is continuous into the oesophagus. '^-^ 

 Its lateral borders may be so approximated that it is changed into a canal. 

 This apparatus is certainly very serviceable to these animals in sucking 

 their prey, after it has been punctured repeatedly, and taken into the 

 mouth. 



With very many Arachnoidae, the food, before reaching the proper 

 digestive tube, traverses a very short oesophagus. '■^^'> 



With the Araneae, this canal is geniculate, of a horny consistence, and, 

 at the point where it enters the stomach, it presents a prismatic muscular 

 enlargement on which is inserted a large muscle arising from the centre 

 of the dorsal shield and passing through the central opening of the 

 stomach. *"> This serves probably as a sucking apparatus during the pre- 

 hension and deglutition of food.'^-'^ With the Tardigrada, the cesophagus 

 terminates also by a muscular apparatus of this kind, which, with Macro- 

 biotus, and Emydium, is spheroidal, and mthMünesium, cylindrical. '^^^ 



§307. 



The Intestinal canal of the Arachnoidae is formed after two difi'erent 

 types. 



1. With the Tardigrada, Acarina, Pycnogonidae, Opilionina, Solpugi- 

 dae, and Araneae, the stomach has a greater or less number of caecal 



9 See § 315. oesophagus of the Pycnogonidae; but, subsequently, 



10 See Treviranus, Bau d. Arach. Taf. II. fig. he found that he was deceived, and that vibratile 

 14-16, r., and Brandt, Mediz. Zool. 11. Taf. XV. organs were wanting here as with all llie Arthro- 

 fig. 9, 18, b. jjoda. 



il Witli the Araneae, and Scorpionidae, the H Brandt, Mediz. Zool. I. p. 89, Taf. XV. flg. 



entrance of the mouth has a tumid, pilose upper 6, b., or Ann. d. So. Nat. XIII. p. 183, PI. IV. fig. 



lip. With the Opilionina, there are several such 2. b. 



tumefactions, but with the Pycnogonidae, the oral 15 This suctorial apparatus appears to have been 



orifice is prolonged, snout-like, between the mux- well described and understood by fVasmann (loc. 



illae. cit. p. 10, fig. 13, i. m.) ; but, already before this, 



12 See Lyonct, loc. cit. p. 401, PI. XXI. fig. 4, Lyonet (loc. cit. p. 402, PI. XXI. fig. 4, C I) E.) 



5, and /j!(«-^.<r, Ann. d. Sc. Nat. VI. p. 178. had rightly perceived it; while Bratult (Med. 



!•'( With the Acarina, Pycnogonidae, ami Araneae. Zool. IF. p. 81) had taken it for an os lii/nules. 



Quatrefa^es (Compt. rend. XIX. 1844, p. 1152) 10 i^oy^rc, loc. cit. p. 322, PI XIII.-XV. 

 tliiiiks he has observed a ciliated epithelium in the 



