ORDERACTINOIDEA. 69 



The Caryopliyllife* afford still other examples of segregate zoo- 

 phytes, with convex forms, arising from the budding function being 

 received equally and retained indefinitely by each polyp. The mul- 

 tiplication of lateral buds causes the ascending stems to diverge, 

 and the clump becomes rounded above. Yet the outer portions of the 

 clump, owing perhaps to their receiving first the waters around, often 

 extend a little the most rapidly, and the form becomes thus flattened 

 convex, rather than regularly hemispherical. The spaces between 

 the branches are quite uniform in the same species, as well as the 

 length of interval between successive buds from the same branch. 



70. A budding cluster. But when with an acrogenous mode of 

 growth, the polyps, after a certain age, lose the function of budding, 

 the zoophyte, commencing as a small hemisphere, lengthens upward 

 into a cylinder, whose diameter is determined by the breadth of the 

 budding duster. This cluster constitutes the extremity of the stem 

 or branch, and, as it is constantly forming new buds, the older polyps 

 of the cluster, at the same rate, are turned out, and joined to the 

 lateral non-budding polyps of the branch. By this process, the branch 

 continues to elongate. The Porites, Sideroporse, and Pocilloporae, 

 afford examples. 



Stems produced from a budding cluster have generally rounded or 

 flattened summits. Exceptions to this are found in some Seriato- 

 porre. In these species, the budding cluster is quite small, contain- 

 ing but six or eight polyps; the three or four alternate push out buds 

 nearly simultaneously at the very apex, and then the others, another 

 set beyond these, each set constituting successively the apex, which 

 is consequently pointed. In some Gorgoniaj, also, in which the 

 budding cluster is very small, the stems are pointed. 



71. Budding fi-om an apical or parent-polyp. Instead of a budding 

 cluster, the Madrepores and Dendrophyllise have a single budding or 

 parent-polyp at the apex of each branch, from the sides of which the 

 lateral buds are given out. 



This is shown in the following figure of a Dendrophyllia. The 

 terminal polyp is the parent from which all the polyps of the branch 

 have proceeded. 



Each branch of a Madrepora, in the same manner, has its parent- 

 polyp. In these genera, the branches have a conical or tapering 

 extremity, while in those which grow and bud from a cluster, 



* The Cladocorre of Ehrenberg. 

 18 



