§ 41. THE POLYPI. 49 
while the tentacles, in the cavities of which are regular currents, serve as 
external organs of respiration, similar to branchiae. 
But, if we regard the whole as a true circulation, the contained liquid 
with its corpuscles will be analogous to blood. But this view is opposed 
by the fact that, with Alcyonium, with Actinia, and perhaps many other 
Polyps, there is a true vascular sanguineous system.” 
We ought, therefore, to compare the liquid in question to chyle, which 
passes from the stomach to the general cavity of the body, in the Bryozoa 
by exosmose, but in the Anthozoa-by the orifices of the stomach.” 
The opinion that these currents form a vascular system, moreover, is not 
reconcilable with the fact that the Anthozoa can at will empty the contents 
of their stomach into it, or in the same way shut off from it the water. 
We are obliged, then, to regard all these cavities as constituting a 
vascular aqueous system, performing a respiratory function, by which, 
in the Anthozoa, all the internal parts are constantly bathed with fresh 
water. This renewal of water is effected by its alternate ingress and 
egress through the stomach,® during which chyle-corpuscles could easily, 
by being mixed with water, be carried into this aqueous system. 
With the Bryozoa, where this system is, without doubt, equally one of 
respiration, we shall have to seek for the openings by which this renewal 
of water takes place. 
These are situated near the anus, and place the 
cavity of the body in direct communication with the external water.*® 
1 See § 39, note 1. 
2 Ehrenberg aud Loven regard the canals of 
the corallum of Campanularia and Sertularia as 
direct prol ions of the h, and designate 
them as intestinal tubes, and their contents as 
chyme. 
8 This alternate ingestion and egestion of water 
has been positively observed by Lister, Lovén and 
Van Beneden, in Sertularia and Tubularia. 
4 By an opening of this kind, Meyen (Isis 1828, 
p. 1228) saw escape the eggs of d/cyonelia stag- 
nalis, which were free in the cavity of the body. 
Van Beneden (Ann. d. Sc. Nat. XIV. 1840, p. 
222) declares that he has observed at the base of 
the tentacles of Alcyonedia a series of orifices, 
* (End of § 41.] In this connection should be 
mentioned branchia-like organs, described by Dana 
oe. cit. p. 42) with the Zoanthina. JA paif of them 
is attached to each of the larger lamelle. He ° 
remarks, “The structure of these organs is such 
that we can hardly doubt their branchial nature ; 
yet no circulating fluid was detected within them.” 
I find no other mention of these parts, except by 
Lesueur (Jour. Acad. Nat. Sc. Philad. I. 183-185, 
Pl. VIII. fig. 1, 5, 9), who regarded them as of an 
hepatic nature. — Ep. 
t [§ 41, note 4.) The true nature and relations 
of the respiratory and circulatory systems of tho 
Bryozoa are yet imperfectly understood, There 
can be but little doubt that water is by some means 
introduced into the general cavity of the body, ani 
there mingles with the nutritive fluid, which trans- 
5 
which may be called aquiferous mouths, for by 
them the water enters the cavity of the body. 
This is perhaps the case with Actinia, also; for 
Rapp (Web. die Polypen u. die Aktinien, loc. cit. 
p. 47) has here found numerous small orifices 
scattered over the whole surface of the body, and 
through which are emitted jets of water when the 
animal is squeezed, thus showing that they belong 
to an aquiferous system. It is quite improbable 
that the hollow tentacles of Actinia are open by 
an orifice at their apex for the circulation of water, 
as many naturalists have supposed. Quatre- 
Jages (Ann. d. Sc. Nat. XVIIL. p. 96) is quite 
opposed to this opinion. See also above § 36, 
note 1.f 
udes through the walls of the alimentary canal. 
But the apertures for the introduction of this water 
have not yet been clearly seen. It is true that 
Wan Beneden thinks he has found “ Bouches aqui- 
féres,” as above d, but their exi 
there has not been fully verified, an) is even 
denied by Allman. At present, therefore it cannot 
be said that the Bryozoa have a true aquiferous. 
system, like the Anthozoa. The perigastric fluid 
is, separated from the water, most probably the 
elaborated product of di , and the corpuscl 
therein d_ chyle-corpuscl Allman’s 
view, therefore (Report Brit. Assoc. 1850, p. 319), 
appears the most correct: “The perigastric circu- 
-lation, therefore, unites in itself the triple function 
‘op al chyliferous, sanguiniferous and respiratory 
system.” — Ep. + 
