100 J. G. WALLER ON AN UNDESCRIBED 



that the former can retain its place as a species, nor do I believe 

 that, had Dr. Bowerbank lived to see such facts as I have stated, 

 he himself vrould have retained it. The new sponge has much 

 in common with it in general mode of growth, especially in the 

 young condition as above described. The fasces proceed in one 

 direction from a base. They spread out birch-like in form, and 

 have precisely the same kind of spicules in the skeleton. Nothing 

 but the microscope could have separated the two, yet that also dis- 

 tinctly allies it to the group of Raphiodesma, to which both must 

 now be referred. 



The sponge in question was found sessile upon a small pebble of 

 limestone within the roots oi Laminaria saccharina. It is extremely 

 small, only measuring Jin. by \. In this, its dry and well bleached 

 condition, no natural colours are preserved ; it is simply of a creamy 

 white, such as most of the siliceous sponges assume when they have 

 been thrown up on the coast exposed to sun and air. "We lose, 

 therefore, all features but those of its intimate structure, which 

 makes it a subject for the microscope. Its general aj^pearance under 

 examination is confused. But this confusion, nevertheless, has an 

 order, and, although it may sound paradoxical, is the result of 

 order. The fasciculi, which seem as if culminating one over the 

 other, forming a ridge in the most developed part, nevertheless 

 obey a law which dictates their progression in one direction only 

 from a base, following nearly a right line from it. Nor do they ever 

 reverse their route in an opposite direction (Fig. 2). And in this 

 they conform exactly to the rule obeyed in the sponge I have pre- 

 viously spoken of as H. macilenta. But, as I have shown, that as 

 different layers start from another base, they will naturally cover over 

 the one beneath at a different angle, so, in the end, the whole mass 

 may assume an heterogeneous mixture apparently devoid of order. 



As the sponge was not found in a fresh condition, one is not able 

 to pronounce an opinion as to the distribution of either oscula or 

 pores. None of the latter are visible, but there are indications of 

 some of the former, though not very conspicuous. The whole of the 

 membranes, which are pellucid, are thickly matted with fine hair-like 

 acerate spicules, somewhat flexuous, as is generally the case when 

 such are delicate in form. These spicules, abundantly interwoven 

 together, (Fig. 5) and combined by a very large number of minute 

 anchorate forms, quite separate it from any of its congeners, though 

 it is intimately allied, in general character, to all others of the genus. 

 A portion of the basal membrane shows us the early mode of develop- 



