Mr. J. D. Dana on Zoophytes. 109 



that increase until they consist of two or three individuals ; and 

 there is thence a passage to the Herpetolithi, Eschsch. (Hali- 

 glossae, Ehr.) and Polyphyllia, Q. and G. The simple and com- 

 pound Cyathophylla are other examples of the difficulty of this 

 separation. 



2. But the modes of budding and growth are of higher cha- 

 racter ; especially the distinction of superior and inferior gemma- 

 tion, in the former the buds being terminal or at the summit, and 

 in the latter lateral or basal. It is of little importance whether the 

 summit-widening, which accompanies superior gemmation, takes 

 place in the discs, or just exterior to the discs. In either case, 

 the visceral lamellae are prolonged at top beneath the upper sur- 

 face by the process of growth, and hence such species have the 

 upper surface of the corallum lamello- striate. 



3. In superior gemmation, when the discs widen and bud, they 

 sometimes subdivide as each new mouth opens, and sometimes 

 not till several mouths have opened. This difference (distin- 

 guishing the genera Astrcea and Meandrina) is of small import- 

 ance. There are Astrcece in which the discs become 2- or 3-com- 

 pound before they subdivide ; and thus the two genera graduate 

 into one another. There are simple and meandrine Mussce, Oken 

 (Lobophyllise, BL), between which no line of separation can be 

 drawn, and they have been always retained in the same genus. 

 The Monticularice, in the same manner, are related to the Mean- 

 drina*. 



4. There is a group of species having superior gemmation, in 

 which the discs have no proper limits ; and in the compound spe- 

 cies the surface is a single disc with many mouths and scattered 

 tentacles (the latter often obsolescent) . The Fungice arc examples 

 of simple species of this kind ; and the Polyphyllia, Pavonice, &c. 

 (including the Astrcea siderea) are compound species. The co- 

 ralla of compound species are characterized by the continuation 

 of the lamellae of the stars from centre to centre, without inter- 

 ruption along a medial line ; and they have no cells except it 

 arise from a prominence of the intervals between the polyp - 

 mouths. They thus differ from the Astrcece ; for the cells in the 

 Astrcece correspond to the visceral cavities of the polyps. 



5. Growing free or attached is a character of minor import- 

 ance. It is sometimes a convenient generic distinction, as with 

 the Fungidce, but in other cases cannot be appealed to. All spe- 

 cies, as is well-known, are attached in the young state ; and the 

 time of becoming free varies with the species, some earlier and 

 some later. The Flabella thus pass so gradually to attached 

 species, and the animals in the two cases are so completely iden- 



* See on this subject Report on Zoophytes, pp. 76, 77. 



