PREFACE. 
V 
the Animal Kingdom. The minute Hydroidea, and some Caryophylliae 
and Alcyonaria are found in the European seas ; and this part of the 
subject has been wrought out with great beauty and minuteness by 
different investigators since the time of Trembley and Ellis. But the 
vast majority of the larger coral zoophytes are in remote regions, and 
require a patient residence upon the spot to study out their living forms. 
The voyages of Peron and Lesueur, and Quoy and Gaymard, together 
with the journey of Ehrenberg to the Red Sea, give nearly all hitherto 
known with regard to them. It is, therefore, no presumption on the 
part of the author to say that a large amount of new information was 
obtained, nor a fact which might not have been anticipated, that such 
information has detected numerous errors in the received systems or 
suggested changes of fundamental importance. In making out the Re- 
port, it was found impossible, in many genera, to describe the discovered 
species wdthout giving new and more definite characters to the old ; and 
the genera themselves sometimes required a modification of their limits, 
and changes in their associations. In every part of the subject, a thor- 
ough revision seemed desirable ; for only by such a course could the 
facts obtained be clearly or satisfactorily set forth. The Report, there- 
fore, has necessarily become a Treatise on Zoophytes. Various collections 
in our country have been consulted in the course of its preparation, 
among which are Peale’s Museum, at Philadelphia ; the Cabinet of the 
Academy of Natural Sciences, in the same city ; and that of the Natural 
History Society of Boston : ail were liberally thrown open, and every 
convenience given to aid in the researches. It will appear, from the re- 
sults, that the plan adopted Vv^as the only one that could have done justice 
to the department of Zoophytes in the Expedition, and honor to the 
country which had contributed so largely in her appropriations to the 
promotion of science. Out of the four hundred and eighty-three species 
of zoophytes in the tribe Actinaria, (exclusive of the Actiniae,) which the 
Report contains, but two hundred and fifty-four, or little more than half. 
