RADIATA. 35 



been originally two inches in diameter, and that had somehow contrived t,<» 

 swallow a valve of Pecten maximiis of the size of an ordinai-y saucer. The 

 shell, fixed within the stomach, was so placed as to divide it complete! v 

 into two halves, so that the body, stretched tensely over, had become thin 

 and flattened like a pancake. All communication between the inferior 

 portion of the stomach and the mouth was, of course, prevented ; yet. 

 instead of emaciating and dying of an atrophy, the animal had availed itself 

 of what undoubtedly had been a very untoward accident, to increase its 

 enjoyments and its chances of double fare. A new mouth, furnished with 

 two rows of numerous tentacula, was opened upon what had been the base, 

 and led to the under stomach ; the individual had, indeed, become a sort of 

 Siamese twin, but with greater intimacy and extent in its unions !" 



The Actiniae are hermaphrodite ; the reproduction is both by division and 

 by eggs ; and the eggs or young (as the case may be) are ejected through 

 the mouth, or rarely, by a kind of abortion, through the tentacles, according 

 to Contarini. The young do not differ essentially from the adult, the chief 

 difference being in the small number of their tentacles. 



The Actiniae reproduce lost j^arts, especially the tentacles, with great 

 facility ; and when the body is cut into two, three, or even four parts, each 

 may survive and become a complete animal. If the section is horizontal, 

 the lower part acquires a new mouth and tentacles, and the upper part a 

 new base, although in one instance the latter produced a second mouth, so 

 that food was taken at both extremities of the new animal. These 

 experiments indicate that the base has the greatest vital power. (See 

 Contarini, Trat, delle Attinie^ &c., Agassiz's Lectures, and Johnston's Zooph. ) 



Actiniae will survive after being placed in water hot enough to blister the 

 skin, and they may be frozen and thawed with impunity, but immersion for 

 a few minutes in fresh water kills them. 



The order Actinoida contains the sub-orders Actinaria and Alcyonaria, 

 and the families, according to Dana, are as follows : 



Sub-order 1. Actinaria. 



Often coralligenous, cells lanielliradiate. 



Tribe 1. Astneacea. 



Many tentacles in imperfect series ; coralla calcareous, with multiradiate 

 cells, with the lamellae extending beyond the cells. 



T'am. 1. Actinidce. Not coralligenous, usually attached, but sometimes 

 floating in the sea. Actinia {pi. 77, ßgs. 5, 8). Lucernaria {pi. ^Q^ßg. 72). 

 ( Johnst. Zooph., p. 228. E.. An. pi. 63, with anatomical details.) 



Fam. 2. Asti'ceidcB. Coralla calcareous, tentacles marginal, coralla with 

 excavate cells, stars circumscribed. Astrea astroites {pi. 75, fig. 62). 

 Meandrina lahyrinthica^ Linn. ( j!?Z. 75, fi^. 64) ; hemispherical, with long 

 winding lines : American seas. 



Fam. 3. Fungidm. Disks not circumscribed, tentacles scattered, short, 

 or obsolete; simple or aggregate-gemmate ; when aggregate the disks are 

 confluent ; surface of the coralla stellate, without proper cells. Fungia, 

 fungites., Linn. {pi. 75, fig. 65), has a circular coral, with radiating 

 lamellae, like the under surface of some mushrooms ; beneath granulated. 



239 



