82 COELENTERATA—CNIDARIA SUB-BRANCH II 
same time mark off the boundaries between which new cycles of successively six, 
twelve, twenty-four septa, etc., are inserted. The septa of any cycle are usually 
all of about the same length and thickness, those of the later cycles being almost 
invariably of lesser proportions than those of the earlier. This law of septal 
growth, however, which was first accurately determined by Milne-Edwards and 
Haime (Fig. 130), is by no means strictly adhered to. Irregularities in the 
growth of new septa may result in a penta-, hepta-, or octameral arrangement. 
Reproduction takes place either sexually, when separate individuals are pro- 
duced ; or asexually, by means of lateral or basal gemmation ; or by fission. In 
composite coralla, the individual corallites are sometimes united by a common 
coenenchyma. Endothecal structures are frequently present in the form of 
synapticula, dissepiments, and tabulae. 
The order of stone corals or Madreporaria (Zoantharia sclerodermata) was 
divided by Milne-Edwards and Haime into five sub-orders: Lugosa, Tabulata, 
Tubulosa, Perforata, and Aporosa. Of these, the Rugosa have been elevated by 
Haeckel into a separate sub-class under the name of Tetracoralla. ‘The groups 
Aporosa and Perforata are called Hexacoralla ; while the affinities of the Tabulata 
(with which the Tubulosa are now generally included) are still unsatisfactorily 
determined. The group is certainly composed of a varied assemblage of forms, 
some of which have been assigned to the Hexacoralla, some to the Octocoralla, 
and some to the Hydrozoa and bryozoa. 
[Miss Ogilvie, D.Sc., will shortly publish a work on the “Structure and 
Classification of Corals,” in which the subdivisions of the Jadreporaria into 
Tetracoralla and Hexacoralla ave entirely abandoned, on the ground that the /etra- 
meral septal system is merely an ancestral feature strongly marked in certain 
of the older families, while heaameral septal symmetry is but one of many forms 
of radial symmetry (pentameral, octameral, decameral, dodecameral, ete.), 
developed in the course of time within this group of corals. The further sub- 
division of Hezacoralla into Aporosa and Perforatu is also discontinued by Miss 
Ogilvie, who classifies the whole of the Madreporaria (“stone corals”) into a 
number of families of equal rank. These are :—Zuphrentidae, Cyathophyllidae, 
Amphiastraeidae (a new family of Palaeozoic—Recent age, including Stauria, 
‘lumnaria, Pinacophyllum, Amphiastraea, Aplosmilia, Euphyllia, ete.), Turbinolidae 
(including the Cyatharonidue and Trochosmilinae), Oculinidae, Pocilloporidae (in- 
cluding the Stylophorinae with the genera Astrocoenia and Stephanocoenia), Madre- 
poridae (including the Turbinarinae), Stylinidae, Astraeidae (excluding the Lus- 
milinae, Edw. and H.), Fungidue (including the Thanmastraeinae), Kupsammidae 
(including the Stylophyllinae, Epistreptaphyllum, Diplaraea, etc.), Archaeocyathidae, 
and Poritidwe.—TuE AUTHOR. | 
Order 1. MADREPORARIA. Milne-Edwards. 
Radially symmetrical sclerodermous corals with typically hexameral (rarely penta- 
meral, heptameral, or octameral) arrangement of septa. 
Sub-Order A. APOROSA. Milne-Edwards and Haime. 
Septa and theca compact ; interseptal loculi usually partitioned off by dissepiments 
or synaptioles, more rarely by tabulae, seldom empty throughout. Theca either in- 
dependently secreted, or formed by fusion of the septal edges, or absent. 
