$ 284. THE CRUSTACBA. 337 
Phyllopoda, it is less elongated and has numerous constrictions, thereby 
resembling the following type. 
3. This type, the third, is found with the Myriapoda, and considerably 
resembles that of the so-called Dorsal Vessel of the Insecta. With the 
Chilognatha, and Chilopoda, it consists of a more or less articulated tube, 
occupying the whole dorsal line of the body. It is divided by constric- 
tions and imperfect muscular septa into chambers, nearly as numerous as 
the segments of the body. Each chamber is attached, as with the Insecta,. 
right and left to the internal surface of the segments of the body, by tai- 
angular muscles. The Diastole is produced chiefly through these muscles. 
At its anterior extremity, this dorsal vessel passes through an Ostiwm arte- 
riosum into an aorta, while, from the posterior extremity of each of these 
chambers are given off two lateral arteries. The returning blood enters the 
heart through the two venous orifices on the dorsal surface of each compart- 
ment, The Systole consists of an undulating action from behind forwards, 
and the blood is thereby propelled partly from one,chamber to the next 
forward, and partly into the lateral arteries, 
§ 284. 
The Circulation outside of the heart, with the Crustacea, has very varied. 
relations, as has already been mentioned. With the lower Crustacea, with 
the Siphonostoma, the Lophryopoda, and the Phyllopoda, the blood forms 
regular currents in the intervisceral lacunae and interstices, but there is no 
trace of vascular walls. The aortic current, shortly after leaving the heart, 
divides into a right and left portion, which, also, sub-divide, enter the 
appendages of the cephalic extremity, then turn and run along the abdom- 
inal surface of the body — furnishing, in their course, several lateral, loop-_ 
like currents, which enter the locomotive organs, then turn again towards. 
the posterior extremity of the back, where they enter the heart, 
Tl. fig. 1, and especially Audouin and Milne Ed- 
wards, Ibid. XI. 1827, p. 376, Pl. XXXIL These 
last naturalists have very distinctly represented 
the dorsal venous orifices of the heart just men- 
tioned. ‘ 
5 With Branchipus, Artemia, Isaura, and 
Apus, the heart which has several constrictions 
and whose venous orifices are very apparent, occu- 
pies the entire dorsal median line excepting in the 
caudal extremity ; see Joly, Aun. d. Sc. Nat. 
XIIL. p. 239, Pi. VIII. fig. 4, j., XVII. p. 307, Pl. 
IX. fig. 43, v.35 also Krohn, Froriep’s neue Not. 
XLIX. p. 305, fig. 1,2; and Zaddach, loc. cit. p. 
17, Tab. I. fig. 17, C., Tab. IL. fig. -14.* 
6 Although Treviranus (Verm. Schrift. II. p. 
81, Taf. VI. fig. 6), and Kutorga (loc. cit. p. 18) 
have, indeed, furnished some communications on 
the heart of Lithobius and Scolopendra, yet we 
are really indebted for what is known of the struc- 
ture of this organ with the Myriapoda to the excel- 
Jent researches of Newport ; see Philos. Trans. 
XXIII. p. 272, Pl. XIII. fig. 18-22 (Scolopendra), 
* [ § 283, note 5.] See also Leydig, loc. cit. Sie- 
bold and Kélliker’s Zeitsch. IIL. p. 287 (Artemia 
nd Branchipus).— Ep. 
‘ +[§ 234, note 1.] This statement of the com- 
plete absence of true vessels in Argulus, is con- 
firmed by the researches of Leydig (loc. cit. 
29 
and fig. 25 (Scutig.,u). According to these in- 
vestigations, the interventricular septa are scarcely 
developed wit: the Chilognatha, although very 
much s° 7h the Chilopoda. 
1 ‘u extra vascular circulation has been ob- 
served with the Lernaeodea, by Nordmann (loc. 
cit. p. 73, 98), and with the Caligina, by Picker- 
ing and Dana (Isis, 1840, p. 205, 1841, Taf. IV.). 
Jurine (loc. cit. p. 437, Pl. XXVI. fig. 8), and, 
with more exactness, Vogt (loc. cit. p. 9, Taf. I. 
fig. 10), have described the circulation with 4rgu- 
lus. For that of Daphnia, see Gruithuisen, 
Nov. Act. Nat. Cur. XIV. p. 403, Tab. XXIV. fig. 
6; Perty, Isis, 1832, p. 725, and Ehrenberg, 
Abhandl. d. Berl. Akad. 1835, p. 189, note. Zad- 
dach (loc. cit. p. 23, Tab. I. fig. 17) has repre-~ 
sented in much detail that of Apus. In order to 
be convinced of the entire want of vascular walls. 
with the lower Crustacea, there is perhaps nc 
species which will serve better than Argulus foli- 
aceus Whose body is wholly flattened and trans— 
parent throughout. ft 
Siebold and Kélliker’s Zeiisch. II. p. 337) upon 
this same species. His schema of the circulation 
with these animals is as follows: ‘‘The blood is 
thrown from the heart into the interstitial lacunae 
of the organs; thereupon it is collected in the 
posterior portion of the heart; a portion of it 
