340 



THE CRUSTACEA. 



^285. 



CHAPTER VII 



EESPIRATORY SYSTEM. 



§ 285. 



The majority of Crustacea respire by Branchiae ; but among the lower 

 orders, there are many which have no trace of respiratory organs, while the 

 Myriapoda respire by aeriferous tracheae. 



With most Siphonostoma, Lophyropoda, and many Stomapoda, there are 

 no particular respiratory organs, the respiration being, therefore, cutane- 

 ous ; and with some species of these orders, the water is renewed by the oar- 

 like action of some of the locomotive organs/^* 



The Branchiae of Crustacea are sometimes lamelliform, sometimes cylin- 

 drical, and often appear either distinct and separate, or consist of compound 

 serrated organs, branched in various ways, on which the branchial lamellae 

 are disposed in a regular row, and the branchial tubes united in larger and 

 smaller tufts. But these lamellate or tubular branchiae are invested with 

 a membrane so thin that it widely diifers from those of the other regions of 

 the body. It is never ciliated, and is usually without fringes, bristles, &c. 

 The interior of these organs presents only a few parenchymatous points, 

 and, whatever may be their form, they are always traversed by numerous 

 canals and large interanastomosing lacunae, which are wholly without 

 proper walls, and are filled by the arterial and venous currents. '-> 



The branchiae are often in connection with their neighboring append- 

 ages. These last consist of multi-articulate lashes or cirri, or of scales, or 

 large plates, and serve either as gyratory organs, or as opercula shielding 

 the respiratory organs ; sometimes, indeed, they perform both of these 

 functions at the same time. Nearly always these organs are fringed with 

 long, stifle and often pinnate bristles.''^' 



1 The branchiae are wanting with the Penellina, 

 Lcrnaeodoa, Ergasilina, and with some Caligina. 

 With Daphnia, Lynceus, and some other allied 

 Lophryopoda, the small oar-like feel concealed 

 under the belly are probably designed for the agi- 

 tation of the water, while the two feet projecting 

 in front of the body, and which are larger and 

 usually branched, are the principal swimming, 

 organs. Indeed, even when these animals are at 

 rest, these organs are seen in perpetual motion — 

 thus causing in the cavity of the shell a continual 

 current of fresh water ; this supports the observa- 

 tion of Elirenlierg (in his third Beitr. loc. cit. p. 

 189, note) that, with these Entomostraca, the inter- 

 nal surface of the valves performs the function of 

 branchiae. The active, hairy, clavate corijuscles 

 Inserted on the base of the first pair of feet with 

 Cyclopsina castor, and whicli have been usually 

 reganled as posterior antennae (Mailer, Entomostr. 

 p. 106, Tab. XVI. fig. 5, 6, c., or Jiirine, Hist. d. 

 Monocl. p. 52, PI. IV.' fig. 1, PI. V. fig. 1. b. PI. VI. 

 fig. 13, a.), are nothing liut organs for the agitation 

 of the water. With Cypris, only, are there perhaps 

 special branchial organs. I'hese little animals 

 liave at the base of the posterior pair of jaws two 

 semilunar, pectinated plates, curved upwards, hav- 

 ing completely the aspect of branchiae ; see Ram- 

 dnhr, Beitr. loc. cit. p. 15, Taf. IV. fig. 5, B. and 

 iig. 8, li. ; also Straus, loc. cit. p. 49, PI. I. fig. 

 i, o. and tig. 8, e., or Baird, in the Magaz. of Zool. 



and Bot. I. p. 520, PI. XVI. fig. 8. These organs 

 appear to have been wholly misapprehended by 

 Treviranus (Verm. Schrift. II. p. 5J, Taf. IX. tig. 

 5). With Mysis, Leucifer, and Amphion, there 

 are no traces of branchiae, while with the other 

 allied Stomapoda, such as Alima and P/iyllosoma, 

 they sometimes e.xist in a rudimentary form. As 

 branchiae, have been regarded, also, the articulated 

 processes of the cloven feet of 31 y sis and some 

 other Stomapoda ; but, certainly, they are organs 

 for swimming or for the agitation of the water, and 

 their organization has nothing in common with that 

 of branchiae. 



ii It is owing to this small quantity of paren- 

 chj-ma in the lamelliform branchiae and to the 

 numerous lacunae filled with blood that, when the 

 circulation in these organs is arrested, the two 

 lamellae of which they are composed, separate 

 from each other, and the whole branchia, swollen 

 from accumulated blood, has the form of an am- 

 pulla. The blood then changes its natural color. 

 Tills pathological state may be easily seen with in- 

 dividuals of Asellus, Gammarus, and Apus, when 

 allowed to be a long time dying. These ampullae 

 are violet, with Gammarus ; ancj of a beautiful red, 

 with Apus ; see my note upon the ampullae of 

 Apus cancriformis, in the Isis, 1831, p. 429. 



3 Hairy and bristled appendages of this nature 

 are often taken for branchiae. These organs are 

 not only surrounded by a thick skin which of it- 



i 



