§ 284. THE CRUSTACEA. 339 
With all the Crustacea, the venous currents gradually converge from 
the lower part of the body into various intercommunicating sinuses, situ- 
ated, some upon the median line, and others at the base of the feet.© 
From these sinuses the blood proceeds to the branchiae, and thence into 
the dorsal sinus the walls of which are thin and uncontractile, and within 
which the heart is entirely enclosed. This dorsal sinus is filled during the 
systole, and the arterialized blood which it ‘contains is absorbed during the 
diastole through the venous orifices of the heart, without any aid on the 
part of the walls of the sinus. 
With the Myriapoda, also, the arterial system is highly developed. Not 
only are there numerous arteries arising from the sides of the heart, which 
ramify in the segments of the body, but also, beside an anterior dorsal 
aorta, two other considerable arteries which embrace the cesophagus, then 
bend below and unite to form, on the abdominal cord, a Supra-spinal artery. 
This artery gives off numerous lateral branches, which accompany the 
principal nerves, and terminate, at last, in ramuscules.” 
But what distinguish the Myriapoda from the higher Crustacea, are 
the venous currents, which, equally extra-vascular, do not run towards the 
respiratory organs, but pass directly into the dorsal sinus, and thence are 
absorbed into the chambers of the heart through the venous orifices. 
5 Of the absence of vessels around the venous 
currents one may easily be convinced from an ex- 
amination of small Amphipoda and Isopoda. 
This absence exists also with the higher Crustacea; 
see Duvernoy, Ann. d. Sc. Nat. VIII. 1837, p. 
34, or in Cuvier, Lecons d. Anat. Comp. VI. p. 
404 (Squilla). Iam quite of the opinion of Lund 
and Schultz (Isis, 1830, p. 1225), who have 
bated the opinion of 4 in and Milne Ed- 
wards and have described the venous system of 
the Decapoda as having proper walls (Ann. d. Sc. 
Nat. Pl. XXVI.-XXXI.). But Milne Edwards, 
who, at this time, advocates with so much zeal the 
ewall-less condition of the circulating currents with 
Mollusca, appears, moreover, to entertain the 
-opinion of a similar circulation with the Decapoda ; 
at least, such would be inferred from what he has 
said upon the circulation in general of Crustacea ; 
see Hist. d. Crust. I. p. 101, and Cyclop. loc. cit. 
eile. 5 
: 6 According to Audouin and Milne Edwards 
(loc. cit. Pl. XXVI. fig. 3), the returniag blood 
from the branchiae enters the heart direct through 
inter-anastomosing vasa branchio-cardiaca. But 
this statement has been reasonably doubted by va- 
rious observers, for these naturalists had overlooked 
the sinus which envelopes the heart of the higher 
Crustacea, and receives, first of all, the branchial 
‘Dlood ; see Straus, Considér. &c. p. 345; Lund 
and Schultz, Isis, 1830, p. 1226; and Krohn, 
Ibid. 1834, p. 522. This dorsal sinus has been 
compared sometimes to an auricle, sometimes to a 
pericardium ; but, strictly speaking, neither of these 
comparisons is correct. 
7 The division of the anterior dorsal aorta, with 
Scolopendra,was first noticed by Straus (Considér. 
&c. p. 347). More detailed researches on the arterial 
“system of the same have been published by Ku- 
torga (loc. cit. p. 18, Tab. III.), and Lord (Med. 
Gaz. part VI. vol. I. 1837, p. 892), who were 
chiefly occupied with the supra-spinal artery. But 
of all the observers, Newport (Philos. Trans. 1843, 
p. 274, Pl. III. XIV.) has worked out the arterial 
system of the Myriapoda in the most complete and 
masterly manner. His researches have shown 
that this system is least developed with the Julidae, 
and rises gradually through the Glomeridae and Ge- 
ophilidae — reaching its highest grade of structure 
with the Scolopendridae. Kutorga has entirely 
mistaken the nature of the heart in regarding it as 
a vena cava, and the supra-spinal artery as an 
aorta. Gaede, also (Zool. Magaz. I. p. 108, Taf. 
I. fig. 7, g. f.), is quite in error as to the vascular 
system of Scolopendra ; for he has evidently seen 
the three vessels arising from the anterior extrem- 
ity of the heart, namely : the dorsal aorta and the 
two vessels which, uniting, form the supra-spinal 
artery ; but he has taken them for nerves. 
8 Newport, who has so well observed the circu- 
latory system of the Myriapoda, says nothing of 
veins, and describes the dorsal sinus as a pericar 
dium. 
