ORDER ACTINOIDEA. 



67 



awhile, an adult, and continues the mode of propagation, until lines 

 of polyps are formed ; and these coalesce at intervals, and form a 

 network. The creeping-shoot, in many species, continues growing 

 indefinitely, and sending up buds at intervals, as in fig. 26. 



It is plain, that if the buds passing out from the different sides of 

 the base of each polyp should all coalesce by lateral extension, we 

 should have an incrusting plate instead of a simple thread network. 

 And, moreover, when these animals coalesce also by their sides above, 

 as often takes place, the plate would have a thickness equal to the 

 height of a polyp. These different varieties are all well illustrated 

 among the Zoanthidae, and the last is exemplified in the Palythoa, 

 described in § 30. 



66. The same process is also illustrated in the following figure of a 

 Gemmipora, in which the budding is lateral from near the base of 

 the polyps. The buds open at the margin of the growing plate, and 

 each young animal may be traced within to the preceding, as is 

 indicated by the lines of the cells on the broken edge forming the 



Fig. 27. 



Gemmipora. 



front of the figure. Other instances are found in the genus Mano- 

 pora. Such forms have been called ezplanate or foliaceous. 

 Very different forms result when the buds 



67. 



are not confined to a single side of the parent, as 



in the Gemmipora, just described. In the Ocu- 



linse, they pass out obliquely from different sides; 



each one gives out a bud, and that another, and so 



on successively, somewhat like the budding of the 



Sertularidae (§ 16); and the zoophyte, proceeding 



from the process, is an erect or ascending stem, as 



in the annexed figures of the coralla of two species 



of this genus. Each bud is for a time at the apex, 



but it gradually becomes lateral and then gives off 



another bud from its upper side. Thus bud follows bud, and the 



stem slowly lengthens. In these corals there is often a distinct spiral 



