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 beautifid 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 Corpiis 

 adiposiiin. 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 a central, propelling organ is very rarely absent, and consists of a heart, 

 sometimes round and vesieuliform, 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. The more or less long arteries do not terminate periph- 

 erically in a capillary net-work, but the blood is freely efi'used into the 



9 Fur til« liver of the common crawfish, which is 

 large hut coiitaiiied in the ci-i)hiUi)thurax, see the 

 descrii)ti ms and figures of Roese/, Suckow, 

 Geveke, Brandt, an<l ScA/cm»), also those of Mül- 

 ler (De Gland. Struct, p. 6^). This last mentioned 

 author r punJ the liver confurmahle with that or 

 many of the other Macruraand ISrachyura. Milne 

 Kdwardi (Hist. d. Crust. PI. IV. tig. ö) has found, 

 with M (1 1, a hepatic mass very remarkable in heing 

 syniiiptrically divided into several lobes. With 

 I'agurux, 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 

 jiumer.ms lateral follicles emjity their product ; see 

 a iva7n7ncrdrtmm, loc. cit. p. H6, Taf. XI. fig. 4, 5 ; 

 MuUer, ha Gland. &c. p. 70, Tab. Vlll. fig. 12, 



13 ; and Delle Chiaje, Descriz. &.c. Tav. LXXXVI. 

 fig. 6.* 



1 These fat-globules, of an orange color, are often 

 found scattered about in Cyclops, Daphnia and 

 Üammarus. 



'■i Such lobes and of a blue color are found with 

 Branchipits on the sides of the digestive canal. 

 Other whitish adipose masses form a kind of net- 

 work m-ouud the intestinal canal of Lernnia, Ler- 

 nneocera and Larnproirlena {Rnthk^, Nov. Act. 

 Nat. Cur. XX. p. 121), and Nordmann, loc. cit. p. 

 6, 125, 132, Taf. I. fig. 4, Taf. VI. tig. 4). This 

 last observer has regarded this reticulated mass as 

 a liver. With the Myriapoda, th<se adipose 

 masses are large, lobulated, and occupy quite a 

 space in the visceral cavity. 



*[^ 2S1, note 9.] For the intimate structure microscope, see /vCirfy. Amer. Jour. Med. Sc. 1848, 

 of the liver of Crustacea, as elucidated by the XV. p. 1. — Vo. 



