367 



oat of the genus, aa far as my present knowledge goes, though it would be 

 unsafe to lay this down as final. In that new species, which I had the 

 pleasure of bringing to the notice of the Club, there is a new form of 

 flesh spicule not hitherto seen (Journal, Vol. i., Ser. ii., p. 216). I direct 

 your attention to H. vermiculata and H. stellifera (Brit. Spongiadas, Vol. iii., 

 PI. xxvi, xxvii.), in illustration of foregoing remarks. Very closely allied to 

 this, differing only in degree is Hymedesmia, a name again compounded of 

 Greek elements previously used. It consists only of a basal membrane and 

 a disjointed stratum of fasciculi of spicules. So closely are these allied, 

 that it would be refining, perhaps, too much to place one before the other 

 in organization. But the third of this allied group Microciona (i.e. small 

 columns) certainly advances beyond the previous phases. In this there is 

 a basal membrane upon which, a somewhat symmetrical arrangement of 

 columns, formed of spicules, arises, and its most advanced example is 

 M. plumosa, so called from its feather-like colamns, making a pretty object 

 under the microscope in sections, besides, being in detail, fall of interest in 

 its variety of spicules belonging to the membranes, &c. One of the genus 

 is eccentric in its variations, and is known as M. fictiUa. M. Plumosa is 

 abundantly found on the shores of Tor Bay at low-water mark and in other 

 parts of Devonshire, &c. I picked up a specimen of M. fictitia on the coast 

 of Brighton : for a new species, found at Paighton, see " Journal Q.M.C." 

 Vol. v., p. 1. 



On the principle of development, I now take another group naturally 

 connected together and belonging to the Keratosa. The sponge of Com- 

 merce so well represents this order, I omit here all reference to it, as also to 

 British sponges directly in alliance with it. But there is one sponge, 

 common enough on our south-eastern coast, which belongs to this order, 

 yet shows a curious development, inasmuch as it strengthens its horny 

 skeleton by the ingestion of grains of sand, fragments of spicules, and 

 other extraneous substances. I may here observe, that sponges doing this 

 are very numerous in different parts of the world, and I may give some- 

 thing of a monograph of them to the Club at some future time. This 

 sponge, named for its ugliness " Dysidea," and specifically termed "fra- 

 gilis, ,, because sometimes, in its dried state, it is very brittle, though 

 indeed you may find it also very tough, may be picked up abun- 

 dantly at Brighton after a storm, and, found here, with fibres often very red, 

 possibly from the red Algse of this coast, gives instruction in the way in 

 which it acts in taking up the particles of quartz, &c. I commend it to 

 your notice, for, though ugly externally, a section by polarized light will 

 display as much beauty as you can desire. The fibre will literally sparkle 

 with gems. Next in our order comes " Oplditaspongia" so called from 

 being armed. It is an ordinary horny skeleton, upon which, externally, 

 sharp acute spicules are developed, whether for defensive purposes, as has 

 been suggested, or not, it is not possible for anyone to pronounce. Asso- 

 ciated with its type form 0. seriata is a tricurvate spicule. 



The next allied form has one species which is to be constantly picked up 

 on our southern coast. It is a bx-anched sponge, one of the few to be recog. 



