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AN OUTLINE OF THE COMPARATIVE STRUCTURE OF THE 
SKELETONS OF ZOOPHYTES. 
By Thomas Wright, M.R.C.S., &c. 
Lecturer on Anatomy and Physiology. 
It may be proper to premise, that in the following pages the term “ zoophyte” 
is restricted to those natural groups of the Padiata of Cuvier comprising the 
Sponges and Corals; these two classes of the animal series present so many 
singular characters in common, that it tends to facilitate a knowledge of their 
structure to regard them as a primitive type of animal organisation. Were it 
the object of this paper to shew that such is in reality the case, many striking 
facts might be adduced in support of my opinion, drawn from their internal 
mechanism alone. This, however, is not a theoretical essay, but an attempt to 
describe, in popular language, the simplicity, beauty, and design demonstrable in 
the frame-work of these interesting beings; and as a knowledge of the skeletons 
of all classes is essential to the true study of Zoology, it occurred to the author 
that a general outline of the structure of zoophytes might not prove unacceptable 
to the readers of The Naturalist , leaving to those whose leisure, circumstances’ 
and acquirements may enable them, to fill up the numerous details left untouched 
in the present sketch. Should occasional relaxation from the numerous duties 
of a laborious profession, enable me at some future time to trace another page of 
lovely Nature, I shall then enter upon the consideration of the organs of locomo¬ 
tion of Radiated animals. 
The Spongiaria or Porifera are among the lowest forms of animal life. They 
are composed of an horny frame-work, invested with a simple homogeneous 
gelatinous tissue, which develops innumerable cilia©, the action of which is 
peculiarly adapted to produce currents in the ambient water, and to attract 
animalcules or other organic atoms that float in every drop of the oceanic waters. 
The delicate structure of these simple beings is supported on an elastic horny 
network, which in some genera is consolidated with Silicious, in others with 
Calcareous spiculse. These interesting beings remain rooted to rocks at the bot¬ 
tom of the sea, or hang suspended like living stalactites from the vaulted arches 
of sub-marine caves, or their delicate vegetable forms droop in endless variety 
from the shelving ledges of rocks exposed to the constant agitation of the restless 
waters, which brings their microscopic prey within the influence of the eddies 
produced by their vibratile organs. 
The minute anatomy of the skeletons of this class has enabled zoologists to 
divide it into three orders, the distinguishing characters of which are derived 
from the nature of the indurating earthy material. The Halinida (XocXis, Silex) 
