^286. 



THE CRUSTACEA. 



341 



The branchiae are usually inserted at the base of the anterior true feet, 

 or the posterior false feet, floating freely in the water; or, they are con- 

 tained in a special respiratory cavity, into which water is admitted through 

 various ways. 



§ 286. 



The principal differences observed with the Crustacea in the disposition 

 and structure of their branchiae, are the following : 



1. Many genera of the Caligina and Argulina, have upon various parts 

 of their body, such as the back, the abdomen, and the tail, several thin, 

 simple, naked lamellae, which may be regarded as branchiae.'^' 



2. The feebly-developed branchiae of the Lepadea consist of cylindrical 

 or lanceolate processes inserted at the base of some of the cirrate feet, and 

 curved towards the back of the animal, so that they are always concealed in 

 the cavity of the shell. But the water is renewed upon their surface by 

 the regular movements of the long posterior feet.^-^ With the Balanodea, 

 the branchiae have left the body of the animal, and are developed on the 

 internal surface of the mantle as more or less numerous soft folds or larael- 

 lae/=^' 



3. With the Laemodipoda, and some Stomapoda, the branchial appara- 

 tus is reduced to a few vesicular or cylindrical, sometimes wholly rudiment- 



self would render them unfit for the respiratory 

 function, Ijut they are not traversed except l3y feciale 

 blood-currents which do not enter the bristles or 

 }iairs. From the complete absence of ciliated epi- 

 thelium, the vortex-producing organs are of much 

 importance. On this account, many species with 

 which these organs are wanting, use their feet for 

 this purpose. 



1 Euryphorus has four such pedunculated 

 branchial lamellae on the dorsal surface of the two 

 grand segments of the body. These are what 

 Milne Edwards (Hist. Nat. d. Crust. III. p. 462, 

 PI. X.KXI.K. fig. 1) has called Appendices ily- 

 troides. With Dinematura, the last pan- of feet 

 is changed into two naked, deeply-fissured bran- 

 cliial lamellae (Kroi/er, Isis, ISil, p. 275, Taf. I. 

 fig. 5, i.). With Phyllophora, the braijchial ap- 

 paratus is still more fully developed, for each foot 

 of the last four pairs terminates with two ovoid, 

 glabrous, branchial lamellae {Milne Edwards, 

 loc. oit. III. p. 471. PI. XXXVIII. fig. 14). 

 Tlie two thin, lanceolate caudal lamellae of 

 Argulus, tlirough which pass strong blood-cur- 

 rents interrupted only by some islets of sub- 

 stance, are certainly respiratory organs to which 

 the oar-like organs which Jurine (loc. cit. p. 

 442) has erroneously considered as branchiae, 

 serve as vortex-producing organs. I am yet un- 

 determined if the respiration is performed by these 

 lamellae alone, or in part by the lateral portions of 

 the dorsal shield through which pass numerous 

 blood-cui'rents. But in any case, I cannot beheve 



it possible, as has Vogt (loc. cit. p. 11), that these 

 lateral portions are the only respu-atory organs of 

 these animals.* 



ü In the various species of Lepas, there are 

 from two to five arcuate branchiae which hang 

 from each side at the base of the first pair of cirri. 

 With Cineras, beside the six branchiae, there is 

 one, very short, upon the back of the animal, at the 

 base of the third, fourth, and fifth pairs of feet ; 

 while with Otion, there is a seventh pair inserted 

 on the second pair of feet ; see Mertens in Miil- 

 ler''s Arch. 1S35, p. 51)2 ; IVagner, Lehrb. d. 

 vergleich. Anat. p. 200 ; Cuvier, Mem. loc. cit. p. 

 6, fig. 2, 5, o. p. ^ßurmeister, Beitr. &c. p. 31, 

 PI. I. fig. 14, c. c' and Martin St. Ange. Mem. 

 loc. cit. PI. II. fig. 17, 19, K. K. {Lepas). 



'i These branchial lamellae are extraordinarily 

 developed with Coronula diadema {Burmeister, 

 Beitr. &c. p. 38, Taf. II. fig. 10, a. a). They are 

 few in number with Balanus {Cuvier, Mem. loc. 

 cit. p. 14, fig. 18, c. c ). It is true that Barmeis- 

 ter subsequently (Ilandb. d. Naturgeschioht. p. 

 551) did not regard as branchiae but rather as 

 ovarian sacs, these organs which as to form and 

 position correspond somewhat to the branchiae of 

 certain Brauchiopoda {Lingula). But even if 

 they do serve at the same time as receptacles of the 

 eggs, this would be no reason for refusing to the 

 folds of the mantle of the Balanodea the function of 

 a respiratory -organ, for, with ether lower animals, 

 as for example with the Lamellibranchia, the 

 branchiae serve as receptacles for the eggs. 



* [§ 286 note 1.] Leydig (loc. cit. Siebold and 

 Kölliker^s Zeitsch. 11. p. 337) has carefully exam- 

 ined the intimate structure of these caudal append- 

 ages with Argulus ; they are composed, 1st, of 

 simple glands such as are found under the skin over 

 tiie whole body ; 2nd, of a rich muscular net-work; 



29^ 



and 3rd, of a lacunal net-work {Lückennetz). 

 The glands and the muscles constitute what is de- 

 scribed above as the islets of substance. Leydig 

 denies that these lamellae, thus composed, have, 

 lieculiarly, a gill function. — Ed. 



