$ 63. 67 
colored fluid and colored corpuscles; and these corpuscles are not found 
except in those vessels surrounding the aquiferous canals. 
_ There is no regular circulation, but the shifting motion of the blood 
ae a thither is due to irregular contractions of various parts of, the 
ody. 
THE ACALEPHAE. 
CHAPTER VII. 
RESPIRATORY SYSTEM. 
§ 63. 
The entire body of: the Acalephae is traversed by..canals which receive 
water from the stomach, or directly from without, and which is ejected 
epongtt openings upon the extremity of the bedy and.on the margin of the 
ise. as : a : 
These aquiferous canals are lined with a delicate, ciliated epithelium, by 
means of which-accidental particles of food or feces are quickly removed. 
‘They have -been regarded both:-as digestive and.as sanguineous organs. 
But that they are respiratory organs is highly probable, not only from their 
structure, — the cilia producing a constant renewal of water,—but also from 
the fact that they are surrounded by real sanguineous vessels. 
This aqueous circulation is oscillatory from one side of the body to. the 
other, being interrupted only by those contractions of the body which occur 
when fresh water passes from the stomach into. the. canals.” , 
1 These new details upon the sanguineous system 
of the Acalephae are due to Will (Hore tergest. 
p. 34, and Froriep’s neue Not. No. 599,:1848, p. 
66). In Berge, he has.heen able to clearly distin- 
guish the ‘sides of these vessels from those of the 
aquiferous-canals contained in’ their interior, for.. 
she firgt are covered with numerous red pigment 
cells. ° 
The blood of this animal has a greenish hue, and. 
contains spherical or slightly elongated red corpus- 
eles, with large nucle. ‘ ‘But,'beside these, Wid/ has 
found in. Cydippe, other ,nucieated cells of a green- 
ish color. In Polyxenia, there is no sanguineous 
system separate from the aquiferous canals, which, 
in Cytaeis and Geryonia are quite surrounded by 
them. The vessels of Cephea contain brown cor- 
puscles; and Will has concluded that the reddish 
threads found along the aquiferous canals of this 
animal, and which, Ehrenberg (Abhandl. a. Berl. 
Akad. 1835, p. 195, Taf. VI. fig. 3, $, and Muller's 
Arch. 1834, p. 568) hag taken for striated muscles, 
are really blood-vessels.”, Profound researches must 
decide the real relations of the aquiferous canals to 
the sanguineous system filled with a violet liquid 
of Velella, as described by Costa (Ann. d. Sc. 
Nat. XVI. ‘p. 188, Pl. XIII. fig. 3). It should be 
amentioned that the blood-system of the Acalephae, 
* [§ 62, note 1.] A true circulatory system has 
mot been observed also by Dana (Struct. and 
Class. of Zoophytes, 1846, p. 12), by Forbes (Brit. 
Naked-eyed Medusae, 1848, p. 6), by Agassiz 
{Contributions to the Nat. Hist. of the Acalephae 
of North America, Mem. Amer. Acad. Boston, 
1850, p. 260), and by Busch (Beobacht. tb. Anat. 
which Will has described with so much positive- 
ness, is not verified either by Bergmann or Frey 
and Leuckart (Beitr. p. 38), after numerous: spe- 
cial researches.* i 
1 If, and espétially with the Discophora, these 
canals have been. taken for digestive tubes,, it-is 
because fa:ces and particles of food have been here 
found, and which have been ejected through the 
openings on the borders of the body. But the real 
function of these openings is to discharge the water 
unfit:for respiration.; and.it is only during the in 
gestion of this liquid that these foreign particles are 
thus introduced. This communication between the 
respiratory and digestive systems reminds ‘one of 
the Polyps, where (as in the Anthozoa) the open- 
ings in the stomach allow its contents to pass into 
the cavity of the body, which last may be likened 
to the aquiferous system. On the other hand, the 
opinion that these canals are blood-vessels would 
be supported by ‘the’ Ctenophora, since here they 
are filled with a red liquid ; but, according to Will 
(Hore tergest. p. 34), this liquid is not in these 
canals, but in’ proper blood-vessels surrounding 
them. He denies, also, that these blood-vessels of 
the Ctenophora open upon the surface of the 
body, or that the blood escapes outward mixed 
with feces. . ‘ 
u. Entwick. einiger wirbellosen Seethiere, 1851, p. 
18). It may, therefore, be concluded that these 
animals have no system of this kind, and especially , 
so as Agassiz failed to notice it after the most inti- 
mate research upon the Berdid Medusae (loc. cit. 
p. 313), which were the objects of Wili’s study. 
—Ep. i; 
