^^ 288, 289. 



THE CRUSTACEA. 



347 



CHAPTEB- VIII. 



ORGANS OF SECRETION. 



I. Urinary Organs. 



§ 288. 



As yet, Urinary organs have not been observed with the Crustacea 

 except in the Myriapoda. Here, as with the Insecta, they consist of long, 

 small, brownish vessels, caecal, and describing many convolutions about 

 the stomach and intestine. These Malpighian vessels, as they have been 

 termed, open into the digestive canal at the boundary between the stom- 

 ach and intestine, and secrete as certainly as do those of the Insecta, uric 

 acid.'i^ With the Chilopoda, there is usually one on each side of the 

 pylorus ; but with the Chilognatha, there are two, which open, however, 

 into the intestinal canal by a common orifice.'-' 



It is now undetermined whether these organs exist also in the other fam- 

 ilies of Crustacea. But with some Decapoda, there are certain caecal 

 vessels which are imperfectly known. They open into the intestine at 

 various points between the pylorus and rectum, and a more complete 

 examination may, perhaps, show them to be of a urinary nature.® 



II. Organs of Special Secretions. 



§ 289. 



The Astacina have a very remarkable secretion commonly known as 

 Crabs-eyes. These are a kind of calculi composed of carbonate of lime 



1 For the Malpighian vessels, which were for a 

 long time regarded as biliary canals, see further 

 under the anatomy of the Insecta. 



2 Ramdohr, Abhandl. iiber d. Verdauungsw. 

 &c. p. 149, Taf. XV. fig. 1 (Julus) ; Trevirayiiis, 

 Verm. Schrift. loc. cit. p. 24, 44, Taf. V. fig. 4, Taf. 

 VIII. fig. 6 {Lithobius and Julux), and L. Dii- 

 four, Ann. d. Sc. Nat. loc. cit. p. 86, 96, PI. V. 

 fig. 1, 4 (Lithobius and Scvtip^era). Scutigera 

 differs from the other Chilopoda in having two 

 pairs of urinary canals. 



See also Kutorga, loc. cit. p. 6, Tab. I. fig. 2, 

 and Miiller, Isis, 1829, p. 550, Taf. II. fig. 5 

 (Scolopendra) ; finally Brandt, in Mriller^s Arch, 

 loc. cit. p. 322, Taf. XII. fig. 2 (G/omeris). 



3 Swammerdamm (loc. cit. p. 87, Taf. XI. fig. 3) 

 had already figured, with Pa^urus, a pretty long 

 coecum opening at the posterior extremity of the 

 intestine. With Maia squinado, there are three 

 such pretty long, of which two are inserted on each 

 side of the pylorus, and the third a Uttlc further 

 behind (Milne Edwards, Hist. Nat. d. Crust. I. 

 p. 76, PI. IV. fig. 1, m. n.). Lund (Isis, 1829, p. 

 1302) has also seen two glandular canals rolled up 

 in a knot, wliich open each side of the pylorus, 

 while a third entered the rectum. This last, ac- 

 cording to Cuvier (Lemons d'Anat. Comp. III. p. 



678) is very common with the Macrura, Brachyura, 

 and Anomura, and notably with Astacus Jluvia- 

 tilis, Homarus marinus. Cancer pagurus, Por- 

 tunus puber, and Cancer maenas. But although 

 Milne Edwards admits the same also (loc. cit. I. 

 p. 76), yet it does not appear to be agreed upon, for 

 Meckel (Syst. d. vergleich. Anat. IV. p. 161) con- 

 tradicts Cuvier in this respect, and declares that 

 he has never found this caecum either with the 

 Crabs or with Astacus, Scyllarus, and Palinu- 

 rus, but only with Pagurus, Penaeus, and 

 Palaemon. Duvernoy, also (LeQons d'Anat. 

 Comp. V. p. 228), has not obsei-ved it in the Ma- 

 crura just cited, nor with Galathea squa- 

 mifera, and Palaemon serratus, although he 

 perceived it with Portunus puber directly behind 

 the pylorus, and with Cancer pagurus, near the 

 rectum. Like Milne Edwards (Hist. d. Crust. 

 I. p. 115, PI. X fig. 2, j. (Maia)), I must leave un- 

 determined the point whether or not, this glandular 

 mass which, with the Decapoda, is concealed under 

 the floor of the respiratory cavities in the bottom 

 of the cephalothorax, and which opens externally 

 by an excretory canal between this same cephalo- 

 thorax and the first abdominal segment, — & 

 really a urinary organ. 



