ORDER ACTINOIDEA. 



77 



limits that belongs to the adult animals. In the corallum, it may 

 be seen to begin by the union of two opposite calcareous lamellae, 

 and the gradual formation of other lamellae, each side of the united 

 pair, in completion of the circle in each cell. 



Fig. 35. 



Fin-. 36. 



Fig. 37. 



This process resembles somewhat the spontaneous fission of the 

 monad, and is compared to it by Ehrenberg. From the illustrations 

 given, it appears to be altogether analogous to budding exterior 

 to the disks, and differs only in the position of the point from 

 which budding commences. This subdivision, though sometimes 

 apparently central, yet often separates only a small portion of the 

 parent; and, instead of being a fission of an individual, it results by 

 a slow divergent growth of the parent and bud. In the Meandrince, 

 Merulinae, and others, the disk-buds open successively in long series, 

 without any proper subdivision of the polyps. Moreover, the Astrsea 

 stellulata, A. stelligera, and A. intersepta, bud exterior to the disks, and 

 sometimes also within the disks. The Merulinae occasionally exhibit 

 a few cells very similar to those of the Echinopora?, thus bringing 

 together these two divisions in the Astrsea family. 



c. In the Monticularise, the elongating lines of disks are united by 

 cross-lines, so that the whole surface appears like a single reticulate 

 disk, with numerous polyp-mouths distributed over it, and having 

 small scattered conical prominences, around which the tentacles are 

 clustered. These species are thus closely related to the Meandrinse, 

 and the prominences are the remains of the ridges (plate 1 3, fig. 13). 



78. Relation of the Fungidce to the Astrceidce. In the Astraeidae, the 

 lamellae of the cells, which striate the interstices in massive species, 

 are generally interrupted half-way between adjoining cells, as in fia\ 

 34 : in other words, each polyp has its limits distinctly marked in the 

 corallum. But in the Fungidae, which are closely allied species, 

 there are no cells, and the lamellae are continuous from centre to 

 centre. We are aided in understanding the relation of the two 

 families, by observing that in some Meandrine species, there are 

 along the bottom of the trench, one to three narrow lamellae, running 



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