5/6 DR. J. E. GRAY ON THE CERATELLAD^E. [NoV. 26, 



smaller branches and the cell-like projections on their surface were 

 covered with spines, they could scarcely belong to the " Alcyoniens 

 amies" of M. Milne-Edwards, and they at once differed from all 

 the known forms of that group of animals by the skeleton being 

 formed of horn. 



One naturalist to whom I showed them declared that they must 

 be plants belonging to the Algae. But this cannot be the case ; 

 they have none of the characters, except the mere external form of 

 Algae ; and their external form is as like to that of some corals as 

 to any genus of Algse that I am acquainted with. 



In general appearance they combine with their plant-like form 

 some characters of the spicular alcyonoid polypes, the texture of 

 the very porous coral called Porites, and the horny consistence of 

 the coarser horny sponges. 



After very mature consideration, I am inclined to regard them, 

 until their internal organization and growth is known, and the ani- 

 mal that forms them has been observed and described, as belonging 

 to that very polymorphous group of animals which has been called 

 Sponges. At the same time, I know no group of sponges with which 

 they can be compared. 



If they are sponges, they must be arranged with the keratose 

 sponges ; but, unlike all the known sponges of that group, they have 

 a series of conical protuberances on the sides of the branchlets, which 

 are developed as the branchlets grow in length, just as the cells of 

 Alcyonoids and stony Madrepores are developed by the budding of new 

 cells from the bases of the last formed ones. The branches and these 

 cells are all formed by the projecting terminations of the horny fibres. 



The stem and older branches are formed of hard, horny, trans- 

 lucent fibres, of a nearly uniform cylindrical form, which are very 

 closely united together into a horny network, with very small cir- 

 cular openings in all directions. This network is very like that 

 found in the older parts of the genus Porites among the stony 

 Madrepores ; but in that genus the network is hard and stony, in 

 this it is hard, horny, and translucent. This hard horny network is 

 very little softened by being soaked in water even for many hours. 



The surface of the stem is either smooth and covered with a very 

 large number of very minute, close, cylindrical canals, or with trans- 

 verse ridges of a similar structure to the stem. 



The upper branches and branchlets are chiefly composed of and 

 covered with agglutinated, closely packed, projecting terminations of 

 the horny fibres ; and on the sides of the branches are placed, in a 

 more or less regular manner, a number of small, short, conical or 

 subcylindrical projections, formed of similar spiculum-like fibres, some 

 of which project beyond the tips of the projections. These projections 

 are placed on the side of the branchlet, which also terminates with 

 a similar tuft of spines, the branchlet increasing in length by the 

 development of new tufts or cells from the base of the old one. 



The texture of the stem and branches would lead one to suppose 

 that the entire coral or sponge is covered with sarcode or flesh in the 

 living state, as in Porites and most sponges. True there is not the 



