238 SUMMARY OF CURRENT RESEARCHES RELATING TO 



there is a tendency to form colonics by budding ; tbeso buds, however, 

 never arise directly from the body of the polyps, but from stolons which 

 are tubular outgrowths of the digestive cavity of the polyps ; the highest 

 development is probably that in which a large number of individuals 

 are so distributed that each has an equal share in the nourishment ; 

 this is best seen in the upright arborescent stocks, where the individuals 

 are spirally disposed. But such a colony is only possible if a supporting 

 skeleton be differentiated ; representatives of this typo are to be found in 

 the Gorgonacea. 



The simplest form of colony formation appears to be that in which 

 the stem-polyps give off tubular processes which are outpushings 

 of the body, and the cavities of which are continuations of the digestive 

 cavity of the polyps. On these stolons new polyps arise by budding, 

 and these, again, may produce polyp-forming stolons ; such are found in 

 Jthizoxenia, Cornularia, and some species of Clacularia. A more compact 

 colony is formed when tho base of the polyps, in which the mesoderm is 

 considerably developed, broadens out around the polyp, and contains 

 endodermal tubes from which new polyps arise by gemmation ; they 

 are seen in Clavularia rosea and C. violacea. In these forms the 

 ccenenchym is a thin membrane, but it may become better developed, so 

 that the deeper part of the elongated digestive cavities lie in it, as in 

 Anthelia, Sarcodictyum, and others. 



The colony may become raised up from its base, and differentiated 

 spicules be developed to form a supporting axis ; this is seen in the lower 

 Briareidse, such as Solenocaulon ; in the higher types the axis is more 

 developed, passes into the interior of the colony, and forms a cylindrical 

 rod, which is surrounded by polyp-bearing coenenchym, as in the 

 division Scleraxonia, of which the highest type is Corallium. In another 

 series of forms, the most favourable arrangement of the individuals is 

 effected in another way ; bundles of polyps, the walls of which have 

 thickened into a common mass of ccenenchym, grow out into long tubes, 

 and develope new polyps at various levels ; thus we get lobed forms as 

 in Alcyonium and Lobularia, or tuft-like growths such as in the 

 Nephthyidae. Lastly, there are trunk-polyps whose coenenchym walls 

 are traversed by canals, and which give off long tubes ; in the walls of 

 the axial polyp, small long tubular polyps are budded off, and these 

 again may give rise to small lateral polyps as in Tolesto among the 

 Cornulariidae. As the hollow axial polyp cannot form sufficient support 

 for the development of a broad stock, a solid horny or calcareous mass 

 is developed in the long digestive cavity ; this gradually gives rise to 

 the central axis of the colony, while the lateral mesenterial septa become 

 the vegetative longitudinal canals of the colony, and the mouth and 

 tentacles of the axial individual disappear. These often exhibit a 

 bilateral symmetry. The Pennatulacea do not form fixed colonies as do 

 the Holaxonia (or Axifera). 



The author next points out the modifications undergone by the 

 spicules, and the differentiations which affect the polyps. 



The three divisions of the Alcyonaria — Alcyonacea, Pennatulacea, 

 and Gorgonacea — proposed by earlier writers, are accepted, the last 

 being divided into the Scleraxonia and Holaxonia. 



In the systematic lists which follow, the relations of the genera are 

 indicated, and there are notes on some of them ; the various families are 

 defined. Novel points, in addition to the delimitations of the Scleraxonia 



