DR. A. FARRE ON THE STRUCTURE OF THE CILIOBRACHIATE POLYPI. 419 
The absence of the ciliary character of the arms, in the present case, appears to be 
as uniform as its presence in the former ; and as so much of the economy of the animal 
turns upon this single point, one more characteristic could not perhaps be selected. 
1 propose, therefore, to unite all those animals, which, partaking of the nature of 
Hydra, present this character, into a second class, to which the name Nudibrachiata 
might be applied. 
This class will comprehend the second family of polypes of Edwards, and the Di- 
morphcece of Ehrenberg. The more interesting forms of it have been so well illus- 
trated by the very interesting descriptions and figures of Mr. Lister, in the paper 
already referred to, that I have no occasion to add any here. 
The points in which Nudibrachiata approach nearest to Ciliobrachiata are (with 
the exception of the mere contour of the body), the general habit and mode of growth, 
and the process of reproduction. The former character I have shown to be extremely 
superficial, and one that should be considered as among the least important in a na- 
tural arrangement. It presents but little essential difference in the two classes. In 
the structure, however, of the more solid parts there appears to be a deficiency of the 
earthy material in the lower class, which in the higher is blended in greater or less 
quantity with the horny matter. The gemmiparous and gemmuliparous mode of 
reproduction appears to be similar in the two classes. 
The Nudibrachiata will probably continue to hold that position in the animal 
kingdom which has been usually assigned to the entire class Polypi. 
The class Polypi being* thus deprived of two of its principal divisions, which, 
whilst they resemble each other so much in superficial character, as to require the 
aid of the microscope to distinguish them, in their intimate structure hold the two 
extreme positions ; the third division only remains. But this is by far the most ex- 
tensive, and the animals are seldom or never so small but that their characters may 
be readily discerned by the unassisted eye, while many attain a considerable size. 
This division corresponds with the third family of Polypes of Edwards, and forms 
the Anthozoa of Ehrenberg, (deprived of the Plydrae and Sertularice ,) as last con- 
stituted by him. In this state I shall leave it, merely adding a few remarks on its 
natural affinities which necessarily arise out of the consideration of the two former 
classes, and in order to complete the view of the subject. 
The Anthozoa will comprehend the corticiferous polypes, together with the free 
and associated Actiniae, and indeed all those forms to which the familiar term “Ani- 
mal Flower” has been most frequently applied. 
The body is here distinctly membranous, and the stomach forms a separate pouch 
suspended in its centre. The stomach has but one external orifice, which serves for 
mouth and anus ; but posteriorly it communicates with the main cavity of the body. 
This, in Actinia, is divided perpendicularly by septa, passing from the stomach to the 
sides of the body ; and with the chambers thus formed the short tubular arms that 
are set round the mouth communicate. In these tubular processes a constant circu- 
3 I 
MDCCCXXXVII. 
