34¢ 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 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 differs from those of the other regions of 
the body. It is never ciliated, and is usually without fringes, bristles, &e. 
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, i 
functions at the same time. Nearly a 
long, stiff, and often pinnate bristles. 
1 The branchiae are wanting with the Penellina, 
Lernaeodea, 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 oryans 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 Ehrenberg (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 corpuscles 
inserted on the base of the first pair of feet with 
Cyclopsina castor, and which have been usually 
regarded as posterior antennae (Mulder, Entomostr. 
p. 106, Tab. XVI. fig. 5,6, c., or Jurine, Hist. d. 
Monocl. p. 52, Pl. IV. fig. 1, Pl. V. fig. 1.b. Pl. VI. 
fig. 13, a.), are nothing but organs for the agitation 
of the water. With Cypris, only, are there perhaps 
special branchial organs. ‘These little animals 
have at the base of the posterior pair of jaws two 
semiluvar, pectinated plates, curved upwards, hav- 
ing completely the aspect of branchiae ; see Ram- 
dohr, Beitr. loc. cit. p. 15, Taf. IV. fig. 5, B. and 
fig. 8, L.; also Straus, loc. cit. p. 49, Pl. I. fig. 
4,0. and fig. 8, ¢., or Baird, in the Magaz. of Zool. _ 
indeed, they perform both of these 
lways these organs are fringed with 
and Bot. I. p. 520, Pl. XVI. fig. 8. These organs. 
appear to have been wholly misapprehended by 
Treviranus (Verm. Schrift. II. p. 59, Taf. LX. fig. 
5). With Mysis, Leucifer, and Amphion, there 
are no traces of branchiae, while with the other 
allied Stomapoda, such as Adima and Phyllosoma, 
they sometimes exist in a rudimentary form. As 
branchiae, have been regarded, also, the articulated 
processes of the cloven feet of Mysis and some 
other Stomapoda 5 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, 
2It is owing to this small quantity of paren- 
chyma in the lamellifurm 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. 
This pathological state may be easily seen with in- 
dividuals of 4sel/us, Gammarus, and Apus, when 
allowed to be along time dying. These ampullae 
are violet, with Gammarus ; and of a beautiful red, 
with Apus; see my note upon the ampullae of 
Apus cancriformis, in the Isis, 1831, p. 429. 
8 Ilairy and bristled appendages of this nature 
are often taken for branchiae. These orgaus are 
not only surrounded by a thick skin which of it- 
