A 
834 THE CRUSTACEA. $$ 281, 282. 
reaches even to the tail, pour their secretion, by a short duct, into the 
digestive canal on both sides close behind the pylorus. 
, 
§ 281. 
With many Crustacea, the digestive canal is surrounded with fat-cells, 
the contents of which are often of a beautiful orange or blue color. These 
cells either consist of a few scattered globules,” or are disposed in lobes 
of various forms.” This tissue is undoubtedly analogous to the Corpus 
adiposum, so common in insects. 
' The fat which these cells contain, plays a part, probably, in digestion and 
assimilation ; for with these animals the excess of nutriment is‘deposited as 
fat to be used in times of need, as, for example, during the act of moulting. 
This explains why the quantity found is so variable, or even may be 
entirely wanting. 
’ 
CHAPTER VI. 
CIRCULATORY SYSTEM. 
§ 282. 
Although the blood of Crustacea traverses the body by a very regular 
circulation, yet, as with all the Arthropoda, the vascular system is here quite 
imperfect, the blood-currents not always being contained in proper canals, 
But acentral, propelling organ is very rarely absent, and consists of a heart, 
sometimes round and vesiculiform, sometimes long and tubular. With 
the higher Crustacea, it is the point of departure of an arterial system: 
which, with the lower orders, gradually becomes abortive, and at last en-- 
tirely disappears. 
erically in a capillary net-work, but 
9 For the liver of the common crawfish, which is 
large but contained in the cephalothorax, see the 
descriptions and figures of Roesel, Suckow, 
Geveke, Brandt, and Schlemm, also those of Mu/- 
ler (De Gland. Struct. p. 69). This last mentioned 
author found the liver conformable with that of 
many of the other Macrura and Brachyura. Milne 
Edwards (Hist. d. Crust. Pl. IV. fig. 5) has found, 
with Maia, a hepatic mass very remarkable in being 
symmetrically divided into several lobes. With 
Pagurus, there is, on each side of the pylorus, a 
long biliary Vessel, which extends along the intes- 
tine to the extremity of the tail, and into which 
numerous lateral follicles empty their product ; see 
Swammerdamm, loc. cit. p. 86, Taf. XI. fig. 4, 53 
Muller, De Gland. &e. p. 70, Tab. VIII. fig. 12, 
*[§ 231, note 9.) For the intimate structure 
of the liver of Crustacea, as elucidated by the 
The more or less long arteries do not terminate periph- 
the blood is freely effused into the 
18 ; and Delle Chiaje, Descriz. &. Tay. LXXXVL 
fig. 6.4 
1 These fat-globules, of an orange color, are often 
found scattered about in Cyclops, Daphnia and 
Gammarus. 
2 Such lobes and of a blue color are found with 
Branchipus on the sides of the digestive canal. 
Other whitish adipose’ masses form a kind of net= 
work around the intestinal canal of Lernaea, Ler- 
naeocera and Lamproglena (Rathké, Noy. Act. 
Nat. Cur. XX. p. 129, and Nordmann, loc. cit. p. 
6, 125, 132, Taf. I. fig. 4, Taf. VI. fig. 4). This 
last observer has regarded this reticulated mass as 
a liver. With the Myriapoda, these adipose 
masses are large, lobulated, and occupy quile a 
space in the visceral cavity. 
microscope, see Leidy. Amer. Jour. Med. Sc. 1848, 
XV. p.1.— Bo. 
