^280. 



TUE CRUSTACEA. 



333 



Daphnia, and Aipus, alone, the anterior extremity of the intestinal canal 

 has several single or ramose caeca, the walls of which appear to serve prin- 

 cipally as hepatic organs/'^ With the Cirripedia, similar caeca exist on the 

 stomach,'"' and form, evidently, the transition to the hepatic organs of the 

 other Crustacea, — that is, to an isolated liver with special, though short excre- 

 tory canals. Such an isolated liver occurs with the Laemodipoda, Iso- 

 poda, and Amphipoda, and consists of long varicose caeca arising from the 

 base of the stomach, and accompanying the intestine a considerable dis- 

 tance.''^' 



With the Poecilopoda, Stomapoda, and Bopyrina, the hepatic organs are 

 inserted at various points along the digestive canal.'''*' Finally, with the 

 Decapoda, the liver consists of two glandular masses composed of more or 

 less ramose caeca loosely bound together. Each of these glands, which 

 sometimes occupies only the sides of the cephalothorax, but sometimes, also, 



largest portion of the alimentary canal dotted with 

 small, yellowish-brown follicles, which I can only 

 regard as hepatic organs, although other Zooto- 

 mists consider them as Malpijjhian canals (see 

 § 287). L. Diifour (loc. cit. p." 96, PI. V. fig. 4, 

 B.) has found these follicles in the stomach of Scu- 

 tigera, but did not regard them as hepatic. 



The numerous large cells, which, according to 

 Serres (Ann. du Mus. d'Hist. Nat. XX. p. 250), 

 cover the external tunic of the intestine of Litho- 

 bius, are cortainlj' only follicles of this kind.* 



5 With Daphnia, there are two lateral, back- 

 wardly-curved caeca, which ascend from the ante- 

 rior extremity of the digestive canal towards the 

 dorsal surface of the head ; see Sc/idffer, loc. cit. 

 p. 41, Taf. II. fig. 2, k. k. ; Straus, loc. cit. p. 

 401, PI. XXIX. fig. 6, s. 0. s., and Jurine, Hist. d. 

 Monocl. PI. IX. X. fig. Y, XI.-XIII. With 

 Branchipus, and Artemia (joly, loc. cit.), the 

 anterior extremity of the digestive tube has also 

 two short caeca which, with the glandular tunic 

 with which the remainder of the intestine is cover- 

 ed, should be regarded as a liver. With Argulus, 

 the stomach has two multiramose caeca, which lie 

 in the parenchyma of the body {Jurine, loc. cit. p. 

 441, PI. XXVI. fig. 1-3, 9, or Vogt, loc. cit. p. 8, 

 fig. 1, 9). With Apus, these caeca are given off 

 from the anterior extremity of the digestive canal 

 and do not extend beyond the anterior border of the 

 cephalothorax {Schdffer, loc. cit. p. 70, Taf. V. 

 fig. 15, a. a.). Acooi-ding to Zaddac/i (loc. cit. p. 

 8, Tab. I. fig. 10-13, and Tab. IV.), these caeca 

 contain numerous glandular follicles. t 



6 Beside the figures of these stomachic append- 

 ages in the works of Cuvier, Burmeister, and 

 Martin St. Ange, see also particularly those which 

 Karsten (Nov. Act. Nat. Cur. XXI. p. 301, Tab. 

 XX. fig. 1-t) has given of the hepatic organs sur- 

 rounding the pylorus with Balanus. 



I With Cyamus, there are two long hepatic 

 canals which wind over the digestive canal (Rous- 

 sel de Vauzeme, loc. cit. p. 252, PI. IX. fig. 19). 

 The two stomachic appendages of Idothea which 

 Rathke (loc. cit. p. 121) has taken for adipose 

 bodies, belong to the hepatic apparatus which here, 

 according to my observations (Mailer's Arch. 



* [ § 2S0, note 4.] For the liver of Julus, see 

 Leidy, loc. cit. He says, " At the termination 

 of the proventriculus, there open two biliary tubes, 

 and from it, surrounding the commencement of the 

 ventriculus, is suspended a broad, white, opaque, 

 reticulated band, apparently composed like the 

 rete adiposa of insects." — Ed. 



t [ § 2S0, note 5.] The hepatic nature of these 

 appendages with Artemia and Argulus is denied 



1837, p. 435) consists of three pairs of yellow vari- 

 cose tubes. With Oniscus, Porcellio, Asellus, 

 and Lygidiuni, there are four very long varicose 

 hepatic tubes which open right and left into the 

 pylorus (Treviranus, Verm. Schrift. I. p. 57, Taf. 

 VII. fig. 38, Taf. IX. fig. 50, Taf. XI. fig. 64 ; 

 Brandt, Mediz. Zool. II. p. 75, Taf. XV. fig. 39 ; 

 Lereboullet, loc. cit. p. 130, PI. V. fig. 25 ; Kars- 

 ten, loc. cit. p. 296, Tab. XXVII. fig. 1). Tre- 

 viranus, who did not observe the excretory ducts 

 of these glands regarded them as masses of fat, 

 while Ramdohr (Abhandl. ub. d. Verdauungsw. 

 &c. p. 204, Taf. XXVIII. fig. 5), who, probably by 

 mistake, has figured with Porcellio three similar 

 appendages, has taken them for salivary organs. 

 There are three pairs of hepatic canals with Cymo- 

 thoa {Meckel, Syst. d. vergleich. Anat. IV. p. 154), 

 Aega {Rathki, Nov. Act. Nat. Cur. XX. p. 30, 

 Tab. VI. fig. 16, d. d. IS), and Lygia {Milne Ed- 

 wards, Hist. Nat. d. Crust. PI. IV. fig. 3). I can- 

 not now decide whether Hiella has really only one 

 varicose hepatic tube, or whether the others were 

 overlooked by Straus (loc. cit. p. 59, PI. IV. fig. 

 15). With Gammarus, and the other Amphipoda, 

 I have found two pairs of long hepatic tubes. 



Frey and Leuckart (Beitr. p. 10-t) have found 

 with Caprella, as with Cyamus, two simple hepa- 

 tic coeca. 



8 With Limulus, there are four groups of inter- 

 laced caecal canals situated in both sides of the 

 cephalothorax. The bile is poured into the ante- 

 rior portion of the intestine by four distinct excre- 

 tory ducts, which are widely separated from each 

 other {Van der Hoeven, loc. cit. p. 18, PI. II. fig. 



I, 5, 8). With Squilla, Bopyrus, and Phryxus, 

 the digestive canal has ramose or varicose hepatic 

 caeca on both sides, at irregular intervals, of its 

 whole length {Mailer, De Gland. Struct, p. 70, 

 Tab. IX. ; Duvernoy, Ann. d. Sc. Nat. VI. 1836, 

 p. 243, PI. XV. fig. 1 {Squilla); and Rathk^, De 

 Bopyro et Nereide, p. 9, Tab. I. fig. 7, and Nov. 

 Act. Nat. Cur. XX. p. 47, {Bopyrus and Phryx- 

 us.) The genus Mysis (Frey, loc. cit. p. 19) on 

 the contrary, which has eij^ht hepatic canals open- 

 ing right and left into the base of the stomach, re- 

 sembles again the Amphipoda and Isopoda. 



by Leydig (Ueber Argulus, &c., and Ueber Ar- 

 temia, &c., loc. cit. Siebold and ffo/rtA-f r's Zeitsch. 



II. p. 334, and III. p. 286) on histological grounds ; 

 it is most probable however that they servo as a 

 liver, since fVill {Mailer's Arch. 1848, p. 506) has 

 shown, by chemical analysis, the hepatic nature of 

 analogous caecal tubes with Daptinia and Cyclops. 

 — Ed. 



