84C THE CRUSTACEA. § 285. 



CHAPTER VII. 



RESPIRATORY 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 sepai'ate, 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 membi-ane so thin that it widely differs 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 prgans ; sometimes, indeed, they perform both of these 

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

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



1 The branchiae are wanting with the Penellina, and Bot. I. p. 520, PI. XVI. fijt. 8. These organ* 



Lcrnaeodea, Ergasilina, and with some Caligina. appear to have been wholly misapprehended by 



With Daphnia, Lynceus, and some other allied Treviranu^ (Verm. Schrift. II. p. 59, Taf. IX. fig. 



Lophryopoda, the small oar-like feet concealed 5). With Myxis., Leucifer, and Amphion, there 



under the belly are probably designed for tlie agi- are no traces of branchiae, while with the other 



tation of the water, while the two feet projecting allied Stomapoda, such as Alima and P/iyllosoma, 



in front of the body, and which are larger and they sometimes exist in a rudimentary form. As- 



usually branched, are the princ^jal swimming, branchiae, have been regarded, als'i, the articulated, 



organs. Indeed, even when these animals are at processes of the cloven feet of Mysis and some 



rest, these organs are seen in perpetual motion — otlier Stomapoda ; but, certainly, they are organs- 



thus causing in the cavity of the shell a continual for swimming or for the agitation of the water, and 



current of fresh water ; this supijorts the observa- their organization has nothing in common with tliat 



tion of Ehrenlierg (in his third Beitr. loc. cit. p. of branchiae. 



189, note) that, with these Entomostraca, the inter- '2 It is owing to this small quantity of paren- 



nal surface of the valves performs the function of chyraa in the lamelliform branchiae and to the 



branchiae. The active, hairy, clavate curjiuscles numerous lacunae tilled with blood that, when th» 



inserted on the base of the first pair of feet with circulation in these organs is arrested, the two 



Cyclopsina castor, and which have beeti usually lamellae of which they are composed, separate 



regarded as posterior antennae (MiiWer, Entomostr. from each other, and the whole branchia, swollen 



p. 106, Tab. X\I. fig. 5,0, c, or Jurine, Hist. d. from accumulated blood, has the form of an am- 



Monocl. p. 52, PI. IV. fig. 1, PI. V. fig. 1. b. PI. VI. pulla. The blood then changes its natural color, 



fig. 13, a.), are nothing but organs for the agitation This pathological state may be easily seen with in- 



of the water. With Cypris, only, are there perhaps dividuals of Jsellus, Gammarus, and Apus, wheu 



special branchial organs. These little animals allowed to be a long time dying. These ampullae 



have at the base of the posterior pair of jaws two are violet, with Gammarus ; and of a beautiful red, 



semilunar, pectinated i)lates, curved upwards, hav- with Apus ; see my note upon the ampullae of 



ing completely the aspect of branchiae ; see Ram- Apus cancriformis, in the Isis, 1831, p. 429. 



dohr, Beitr. loc. cit. p. 15, Taf. IV. tig. 5, B. and 3 Hairy and bristled apjK'ndages of this nature 



iig. 8, L. ; also Straus, loc. cit. p. 49, PI. I. fig. are often taken for branchiae. These organs are 



4,0. and fig. 8, e., or liaird, in the Magaz. of Zool. not only surrounded by a thick skin which of it- 



