184 Royal Society : — 



thickening of the calcareous network of those plates, the axial 

 cords come to lie in furrows channelled out in their ventral 

 surfaces; while by a further endogenous growth of that network 

 these ventral furrows are completed into canals ; and it is by a 

 still further endogenous thickening that these canals finally come 

 to occupy the centre of each Radial and Brachial calcareous 

 segment. 



At the same time I would repeat that I see no reason for 

 refusing to believe that the subepithelial band of Ludwig is a 

 sensory nerve, the functions of the single trunk of the Asteroida 

 being here divided between two, an afferent and a motor, just as, 

 in Man, the double function of an ordinary spinal nerve is divided 

 in the head between the 5th and 7th pairs. And it seems not 

 unlikely that while the " axial cords " (motor nerves) of the arms 

 are derived from the peripheral part of the Crinoidal axis, the 

 " ventral bands " (sensory nerves) are derived from the central 

 part of that axis, which has been shoMH to be continued, as the 

 " axial prolongation," to the oral ring. 



June 15, 1876. — Dr. J. Dalton Hooker, C.B., President, in the Chair. 



Preliminary Note on the Structure of the Stylasteridse, a group of 

 Stony Corals which, like the Milleporidae, are Hydroids, and not 

 Anthozoans. By H. N. Moseley, Naturalist on board H.M.S. 

 * Challenger.' 



On 14th February, 1876, in lat. 37° 17' S., long. 53° 52' W., 

 off the mouth of the Eio de la Plata, the trawl brought up from 

 600 fathoms a number of specimens of corals of the family Sty- 

 lasteridae (Gray *). The specimens included six genera of the 

 family, and seven sp'ecies. They were all in most excellent pre- 

 servation, notwithstanding the fact that they had been slowly raised 

 from 600 fathoms ; and all had their generative organs in full de- 

 velopment. An opportunity which had long been desired was 

 thus afforded for making a detailed examination of the structure of 

 the soft parts of this family, which, in the structure of its coralla, 

 shows so many points of variance from that of Zoantharian coralla. 

 From observations made on a species of Stylaster obtained from 

 500 fathoms off the Meangis Islands, and on a Oryptohelia, a short 

 account of which is given in the Eoyal Society's ' Proceedings,' 

 vol. xxiv. p. 63, I had already been led to suspect that the 

 Stylasteridse might prove to be Hydroids — although I did not ven- 

 ture to express this opinion, because the evidence was then insuffi- 

 cient. The examination of the series of forms obtained off the 

 Rio de la Plata at once showed that the Stylasteridae are true 

 Hydroids. 



Unfortunately the trawl came up rather late in the day, and 

 hence a very short period of daylight was available for the ex- 

 amination of the animals in the fresh condition ; but it sufficed for 



» Ann. and Mag. Nat. Hist. vol. lix. (1847). 



