§ 279. 



THE CRUSTACEA. 



331 



nioidae, and Apodidae, on the contrary, its anterior extremity mounts 

 towards the dorsal surface of the head, and then curves backwards to the 

 mouth. <■" 



With the other Crustacea, there is, more or less distant from the oesophagus, 

 a stomach, formed by a jiyloric constriction of the intestine. This stomach 

 is small with the Cirripedia, Laemodipoda, Isopoda, and Amphipoda ; ^''^ 

 but is pretty long with the Myriapoda.^''' In many of the Isopoda and 

 Laemodipoda, the stomachic epithelium has stiff cilia, or presents a carti- 

 laginous, or horny aspect, thus constituting a stomachic support and dental 

 apparatus,® which is also observed in the somewhat larger stomach of the 

 Poecilopoda and Stomapoda.''-" But this structure of the stomach is most 

 prominent with the Decapoda. llemarkable for its size and form, it con- 

 sists of two portions; one, anterior, vesiculiform, communicating with the 

 oesophagus, the other pyloric, pyramidal, and with the apex pointing back- 

 wai-ds. The internal tunic of the stomach is composed of chitine and 

 covered with stiff bristles, or sometimes with groups of very singular hairs 

 of a forficulate form. Moreover, its callous and cartilaginous portions 

 form, in the pyloric region, a remarkable support, on which are three solid 

 movable pieces. One of these pieces is a single tooth placed in the middle 

 of the posterior wall of the stomach; while the other two, longer and 

 somewhat crenulated, are situated on the sides opposite each other. Seve- 

 ral muscles, arising from the internal surface of the cephalothorax, are in- 

 serted on this stomach, and it is very probable that, by these, the animal 

 can voluntarily bring the three pieces together, making them serve as inter- 

 nal masticatory organs.*^"* 



5 For the arcuate intestine of Daphnia, Lyn- 

 ceus, and Polyphemus^ see the figures given by 

 Jurine, Hist. d. Monocl. ; Straus, loc. cit. PI. 

 XXIX. (Daphnia) ; Brongniart, loc. cit. PI. 

 XTTI. (Limnadia) ; Straus, Mns. Seuclcenb. loc. 

 cit. p. 112, Taf. VII. fig. 12, and Jo/y, loc. cit. PI. 



VII. fig. 5 (Isaura). With Cypris, there is a kind 

 of stomach on the curved digestive canal {Straus, 

 loc. cit. p. 60, PI. I. fig. 10). 



B For the intestine and stomach of the Cirripe- 

 dia, see the writings of Cuvier, Burmeister, and 

 Martin St. Ange ; also Roussel de Vauzime, loc. 

 cit. PI. VIII. tig. 12, 18 (Cyamus) ; Brandt, 

 Mediz. Zool. II. Tab. XV. fig. 39 (Oniscus) ; Lere- 

 bouUet, loc. cit. p. 126, PI. V. fig. 25 (Lygidium), 

 and Rathki, loc. cit. Taf. IV. fig. 19 (Idothea). 



' See Ramdohr, Abhandl. iib. d. Verdauungsw. 

 d. Insek. p. 14S, Taf. XV. tig. 1 ; Treviranus, 

 Verm. Schrift. II. p. 23, 43, Taf. V. fig. 4, Taf. 



VIII. fig. 6 (Lithobius and Julus) ; L. Dufour, 

 loo. cit. p. 84, 95, PI. V. fig. 1, 4 {Lithobius and 

 Scutigera) ; Kutorga, loc. cit. p. 6, Tab. I. fig. 2 

 {Scolopendra) ; and Brandt, in Muller's Arch; 

 loc. cit. Taf. XII. fig. 2 (Glomeris).* 



S The stomach of Oniscus contains a cartilagi- 

 nous support of a peculiar form {Brandt, Mediz. 

 Zool. II. p. 74, Taf. XV. fig. 41, 42). That of the 

 stomach of Idothea entomon is composed of seve- 

 ral solid pieces {Rathki, loc. cit. p. 119, Taf. IV. 

 fig. 20, 21). With Lygidium, the epithelium is 

 supported by several horny pieces, and provided 

 with numerous stiff bristles {LerelmuUet, loc. cit. 

 p. 127, PI. V. fig. 26-30). Finally, with Cyamus, 



there are in the cardiac region of the stomach two 

 lateral horny tridentate folds {Roussel de Vauziine, 

 loc. cit. p. 251, PI. Vm. fig. 13, 14). 



9 With Limulus, the tesophagus extends in 

 front and opens into a very muscular backwardly- 

 curved stomach the epithelium of which has fifteen 

 longitudinal rows of horny teeth {Van der Hoeven, 

 loc. cit. p. 17, PI. II. fig. 3. B.). With Squilla, 

 the stomach is pyramidal, and has, at its pyloric 

 region, horny plates and very regular rows of hairs 

 {Duvernoy, in Cuvier^s Legons d'Anat. Comp. 

 V. p. 231). With Mysis, also, tlie epitliellum of 

 the pyriform stomach is supported by several solid 

 lamellae composed of chitine and covered with 

 bristles mixed with hairs {Frey, loc. cit. p. 16). 



10 The stomach of the Crawfish is the one best 

 known ; see the descriptions and figures given by 

 Roesel, Sue/cow, Brandt, loc. cit., and JUj/jie Ed- 

 wards, Hist. d. Crust. I. p. 67, PI. IV. The inti- 

 mate structure of this stomach and its internal 

 ajjpendages have been carefully studied by Valen- 

 tin (Repertorium, I. p. 115, Taf. I. fig. 15-21) and 

 by Oesterlen {Muller's Arch. 1840, p. 387, Taf. 

 XII.). 



The teeth and bristles here observed, are found 

 also with the three divisions of the Decapoda. I 

 have seen them with Homarus, Palinurus, Gala- 

 thea, Pagurus, Cancer, Maia, Lupea, kc. 

 With Crangon, and Palaemon, 1 found the dental 

 lamellae wanting but the epithelium was hairy. 

 With Caridina, according to Joly (loc. cit. p. 73, 

 PI. III. fig. 27), hairs of this kind are inserted on 

 the band-like condensations of the stomach. 



* [ § 279, note 7.] For the alimentary canal of 

 Julus in all its details, see Leidy, A Flora and 



Fauna within living Animals, in Smith.sonian Con- 

 tributions to Knowledge, V. 1853. — Ed. 



