SUBDIVISIONS OF AGTINOID POLYPS. 71 



phorse ; and the branches vary from the flattened and broad 

 form shown in figure 7 (which represents the upper part of 

 a branch of the P. grandis D.), to irregularly cylindrical 

 branches, looking rough on account of the very short branch- 

 lets. The cells are usually stellate, as in figure 8, from P. 

 elongata D., and often one of the septa, and sometimes two 

 opposite ones, extend to a columella at the centre, as illustra- 

 ted in figure 9, from P. plicata D. ; dividing the cell into 

 halves. The cell in the interior of the corallum is crossed by 

 thin plates or tables, as shown in figure 10, and hence they 

 have been called tabulate corals. Agassiz, after the discovery 

 of the Hydroid character of the animals of the Millepore corals, 

 whose cells also are tabulate, referred the Pocilliporae to the 

 same Hydroid type. But the recent study of the polyps has 

 shown that they are true polyps ; and Prof. Verrill remarks 

 on the resemblance of the tentacles to those of the Oculinae. 

 The stellate character of the calicle also proves that the ani- 

 mals must be polyps. 



Madrepore tribe, or Madreporacea. — In this tribe the cor- 

 alla, even to the walls of the corallets, are remarkable for be- 

 ing porous, and the radiating lamellae of the polyp-cells are 

 narrow, often perforated or imperfectly developed, and fre- 

 quently mere points. The coralla are either branched, mas- 

 sive, or foliaceous. Budding is lateral, and in the branching 

 species there is either a parent polyp, as in Madrepora and 

 Dendrophyllia, or a terminal budding cluster. This peculiar- 

 ity has been already illustrated in the figure of Madrepora 

 aspera, on page 50. On the following page there is an out- 

 line sketch of another species, the Madrepora formosa D., 

 common in the Feejees, and also in the East Indies. The two 

 species here mentioned give a good idea of the ordinary char- 

 acter of the Madrepore corals. One of the polyps of the Mad- 



