ORDER ACTINOIDEA., Bil 
ing the single additional function of secreting a Corallum. The 
preceding cut represents the closed and expanded condition of the 
Actinia. Their various and gorgeous hues are finely exhibited in the 
coloured engravings on plates 1 to 5. 
Although these animals are usually attached at bottom, many 
of them may detach themselves and float through the water to a new 
resting-place ; or, they will slide along slowly over the rocks, by the 
action of the base or foot; and some are said to turn over and walk 
on the extremities of the tentacles, which affix themselves by a sucker- 
like action. There is a small group of Actinie (Actinecte), which are 
fitted expressly for an ocean life, by means of an air-cavity in the base, 
containing a vesicular or spongy disk, made up of air-cells, to serve 
as a float. ‘The animal lies in the water with its base uppermost, and 
mouth and tentacles below, and is thus carried about by the winds 
and currents. 
22. Structure.* The exterior of the Actinia is fleshy, or more or 
less coriaceous in texture. Though frequently smooth, the lateral 
surface is sometimes covered with minute warty prominences or 
tubercles ; occasionally it is furnished with small cup-vesicles, which 
adhere by suction like the cups of a cuttle-fish, and, by means of 
them, the animal fixes about it sand and fragments of shells, or aids 
itself in its progressive motions. The tubercles are sometimes dis- 
tinctly perforated, and Lesueur and others have seen the water, from 
within the animal, spurted out through these perforations. Dr. C. 
Pickering compares the ejections of one seen by him abroad, to a 
shower from a watering-pot. Whether these perforations are gene- 
ral in Actinie without vesicles, has not hitherto been determined. 
Evidence of their existence, however, has been distinctly observed 
in the A. marginata of the Boston Harbour, by Dr. Wyman, and 
this species has not the slightest trace of tubercles; the skin is 
fleshy and smooth. ‘They were detected by direct observation with 
the microscope, after having seen currents of water pass from them 
* Dissections and descriptions of Actiniz have been made and published by Spix, Delle 
Chiaje, Lesueur, Rathke, Teale, and Quatrefages. In the account here given, the facts 
have been mostly verified by the author’s observations, or by the skilful dissections of Dr. 
Jeffries Wyman, of Boston. For views of the structure of the spermatic cords, and 
other interesting particulars respecting the Actinia marginata (Lesueur), of the harbour 
of Boston, he is indebted to Dr. Wyman’s microscopic researches, many of which were 
made the past summer, during a short residence of the author in that city ; and wherever 
reference is made above to this species, the observations are those of Dr, Wyman. 
