§ 286. THE CRUSTACEA. 3841 
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 lamel- 
lae.© 
3. With the Laemodipoda, and some Stomapoda, the branchial appara- 
tus is reduced to a few vesicular or cylindrical, sometimes wholly rudiment- 
felf would render them unfit for the respiratory 
function, but they are not traversed except by feeble 
dlood-currents which do not enter the bristles or 
hairs. 
thelj 
From the complete absence of ciliated epi- 
the vortex-prod 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, 
Pl. XXXIX, fig. 1) has called Appendices ély- 
troides. With Dinematura, the last pair of feet 
is changed into two naked, deeply-fissured bran- 
chial lamellae (Kroyer, Isis, 1841, p. 275, Taf. I. 
fig. 5, i). With Phyllophora, the branchial ap- 
paratus is still more fully developed, for each foot 
of the last four pairs terminates with two ovoid, 
glabrous, branchial lamellae (Milne Edwards, 
Joc. cit. TIL. p. 471. Pl. XXXVIIL. fig. 14). 
The two thin, 1 1 caudal lamell of 
Argulus, through which pass strong blood-cur- 
rents interrupted only by some islets of sub- 
stance, are certainly respiratory orgavs 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 
Jamellae alone, or in part by the lateral portions of 
the dorsal shield through which pass numerous 
blood-currents. But in any case, I cannot believe 
* [§ 286 note 1.] Leydig (loc. cit. Siebold and 
Kolliker’s Zeitsch. IL. p. 337) has carefully exam- 
ined the intimate structure of these caudal append- 
ages with Argulus; they are composed, Ist, of 
simple glands such as are found under the skin over 
the whole body ; 2nd, of a rich muscular net-work; 
29% 
it possible, as has Vogt (loc. cit. p. 11), that these 
lateral portions are the only respiratory organs of 
these animals,* 
2In 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 5 
while with Otion, there is a seventh pair inserted 
on the second pair of feet; see Mertens in Mul- 
ler’s Arch. 1835, p. 502; Wagner, Lebrb. d. 
vergleich. Anat. p. 200 ; Cuvier, Mém. loc. cit. p. 
6, fig. 2, 5,0. p.; Burmeister, Beitr. &c. p. 31, 
Pl. I. fig. 14, ¢. ¢., and Martin St. Ange, Mém. 
loc. cit. Pl. II. fig. 17, 19, K. K. (Lepas). 
3 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, Mém. loc. 
cit. p. 14, fig. 18, c.c.). Itis true that Burmeis- 
ter subsequently (Handb. d. Naturgeschicht. 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 Branchiopoda (Linguda). 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 other lower animals, 
as for example with the Lamellibranchia, the 
branchiae serve as receptacles for the eggs. 
and 8rd, of a lacunal net-work (Lickennetz). 
The glands and the muscles constitute what is de- 
scribed above as the islets of substance. Leydig 
denies that these lamellae, thus composed, have, 
peculiarly, a gill function. — Ep. 
