Miscellaneous. 147 



celaia, which, since the time of Grant, has so often attracted the 

 attention of naturalists. In studying these creatures, immersed in 

 the water immediately after they were taken from the dredge, so as 

 to approach as nearly as possible to the conditions of natural life, it 

 appeared to me that we had hitherto described and interpreted in 

 an incomplete manner the nature of the prolongations or papillae 

 which the Clionce emit through the perforations of the oyster-shells, 

 and the very perceptible although not very rapid movements of 

 which have struck all those who have been able to examine these 

 animals. 



The prolongations are of two sorts. Some (the only ones well seen 

 by previous authors) are hemispherical, more rarely cylindrical, and 

 perforated at their summit ; at this point there is, in fact, a wide 

 opening, which may attain as much as 1 millim. in diameter : it is 

 the orifice of a canal traversing the whole papilla and communi- 

 cating with the ducts which in this as in all the other sponges tra- 

 verse the parenchyma in all directions. The prolongations of the 

 second kind, which are much more numerous than the preceding, 

 have an entirely different form, which may be compared to that of the 

 rose of a watering-pot ; they are in the shape of a reversed truncated 

 cone, so that on leaving the perforation they enlarge gradually, and 

 terminate in a very elliptical convex surface ; this is not widely 

 perforated, but presents an elegant network of fibres anastomosing 

 in all directions, which are formed of bundles of spicula covered 

 w^ith sarcode. The fine meshes of this net form so many apertures 

 which open by short conduits into a central canal, situated, as in the 

 prolongations previoiisly described, in the centre of the papilla, and 

 terminating in the same way in the general system of internal irri- 

 gation. 



These second prolongations of the Clionce were certainly seen by 

 Grant ; but he desciibed them as being the transitory state of the 

 papilla just before its opening widely. From my observations, re- 

 peated and followed up long enough to allow me to present them 

 with confidence, this is not the case : the surface of the perforated 

 shell always presents side by side with papillae of the first kind 

 others constructed upon the second type ; and in individuals which 

 I have preserved living and active for nearly twenty days, I was 

 even able to demonstrate that, after taking them from the Avater 

 (which is a certain means of causing the prolongations to be re- 

 tracted), on replacing them in the aquaria after some time, the same 

 perforations always give passage to papillae of the same kind. We 

 might imagine, considering the simplicity of the structure of these 

 creatures, that in certain cases changes might take place ; but I have 

 not observed any. 



We may conclude, from this arrangement, that, in Cliona celaUt, 

 whilst the papillaj with w4de perforations are, as has long been 

 ascertained, the oscula or efi'erent orifices of the current of water 

 which continually traverses the parenchyma of the sponge, the pa- 

 pilke of the second kind bear, collected upon their widened surface, 

 the afferent orifices or pores. It is to be remarked that hitherto. 



