156 Prof. G. J. Allman on the Anatomy of Acteeon. 
extremity of the branchial appendages as M. de Quatrefages de- 
scribes under the name of cloaca*. The length of the cesopha- 
gus and the form of the stomach are altogether at variance with 
his description. The cesophageal collar consists of seven, not 
four, ganglia ; and if to these pomts of discrepancy we add some 
others mentioned in the present paper, and call to mind that he 
has totally overlooked the salivary apparatus and made no men- 
tion of the highly-developed generative system, we cannot but 
conclude that the establishment of a new order of animals on ob- 
servations so imperfect is unwarrantable and rash. 
But suppose the observations of the French zoologist not al- 
together so erroneous as is here maintained, is he yet justified in 
the step which he has taken? We assuredly think not. 
Let us consider for a moment whether the singular ramified 
system connected with the stomach in Acteon and other allied 
genera is really of that vast importance in a zoological point of 
view with which M. de Quatrefages would invest it. If the sy- 
stem in question be merely a ramification of the stomach, we can 
certainly see in it a disposition by which the surface of the gastric 
cavity is greatly increased; but this disposition, exercising no 
marked influence over the organism, cannot be supposed to de- 
mand any important modifications in the other organs, and surely 
offers no solid grounds for believing that its office is to expose 
the products of digestion to the influence of the aérated medium. 
In truth it is ill-adapted to this function, separating its contents 
from the surrounding fluid, not only by its own walls but by the 
intervention of a portion of the cavity in which it floats, and by 
the whole thickness of the integumentary structures. 
But it may be asked, what office is it possible to assign to the 
system now under consideration, if it be not that of respiration ? 
I believe that the ramified apparatus in Acteon and the Holidide 
is truly a hepatic system, and affords an interesting example of 
the reduction of a gland to one of its simplest conditionsf. 
We have in these gastric ramifications one or more offsets from 
the liming membrane of the alimentary canal greatly extended 
* We can in no way explain what M. de Quatrefages intended by the 
organ which he describes as a cloaca, unless we suppose that. he really meant 
the oval sac (y, Pl. VI.) in the posterior part of the body, which we have de- 
scribed in connexion with the generative system, and which by some strange 
confusion he has transferred to the posterior extremity of the branchial ex- 
pansions. 
+ Since the opinions here expressed were laid before the Association, 
there has been placed in my hands anumber of the ‘ Comptes Rendus,’ con- 
taining a paper by M. Souleyet on the Phlebenterata (Annals, xiv. p. 342), 
in which I find that the author’s observations on this subject are entirely in 
accordance with my own. 
a>" * 
