97 



On an Undescribed British Sponge of the Genus 

 Raphiodesma (Bowerbank.) 



By J. G. Waller. 



(Read April 2^rd, 1880.; 



PLATE V. 



During a stay of two months at Torquay, engaged eight hours a 

 day, there was but Httle opiDortunity for recreation in Natural 

 History. Nevertheless, each evening I was down by the sea-side, 

 either at Anstey's Cove or at Meadfoot, and, occasionally, when tide 

 served, at that very interesting spot, Hope's Nose, the eastern 

 promontory of Torbay. Abundance of the Laminaria here often 

 strews the coast, and their roots are incrusted with^ sponges and 

 other organisms. It afforded a very ready means of collection, and 

 thus I became possessed of some rare examples, and of the one, I 

 am about to describe as, new to our fauna, as well, also, of many 

 early states of growth, which is always interesting to observe. 



It was upon a small pebble held in the root grapple of Laminaria 

 saccharina that I found the sponge in question, but before I pro- 

 ceed to describe it, I must call attention to another, found under 

 similar conditions in many different stages of development, and gene- 

 rally in the deepest recesses. It was very small and insignificant, 

 and might easily have escaped attention. When examined, it 

 was seen to be crawling over the rootlets in a very regular manner, 

 sometimes over small pebbles held within them. Upon this one of 

 limestone, we see it in its youngest development, and it is interesting 

 and instructive to note its peculiar mode of growth. It begins 

 with a few spicules, arranged in a somewhat semi-circular form, and, 

 at nearly right angles, are fasciculi of the same disposed with almost 

 rhythmical regularity, with about equal distances between each 

 fascicle ; and thus it proceeds in one direction only, moving for- 

 wards, and never reversing its steps (Fig. 1). This is remarkable in 

 a sessile sponge, which, in general, developes all round from a 

 centre, and spreads in every direction ; it is, therefore, a feature to he 

 noted, as it ceases to be visible, when, in a further development, there 



