1872.] DR. J. S. BOWERBANK ON THE SPONGIAD^E. 633 



constructed honeycomb. On applying to Dr. Lister for an expla- 

 nation of this exceptional condition of the specimen, he stated that 

 the specimens in which the oscula were closed were taken from the 

 sea and dried immediately in a shaded place, and that the one in 

 which they were all open was placed about half an hour after re- 

 moval from the sea in a basin with sea-water sufficient to entirely 

 cover it and was left exposed to the sun. When thus placed, nearly 

 all the oscula were closed ; and it was observed by Dr. and Mrs. 

 Lister that a gradual contraction of the closing membranes very 

 shortly commenced, which continued until the whole of the oscula 

 were open to their greatest extent ; and in this condition they re- 

 mained. Dr. Lister also stated that when attached to the rock and 

 undisturbed the oscula were most frequently open, but that if dis- 

 turbed by being removed from the rock they immediately contracted 

 slowly and became" entirely closed. We are familiar with this de- 

 scription of action in Hymeniacidon celata and other species of 

 sponges ; but there is no one with which I am acquainted that ex- 

 hibits this vital action on so extended and striking a scale as the 

 species under consideration. 



The dermis has a strikingly coriaceous appearance. The dermal 

 membrane is thin and pellucid, and is abundantly supplied with long 

 and slender ovo-spinulate spicula more or less arranged in broad flat 

 fan-shaped fasciculi, in which the bases are all coincident and the 

 apices radiating. There is no difference in size between these spicula 

 and those of the skeleton. The most distinctive character in this 

 species is undoubtedly the very minute but remarkable spinulo- 

 multiangulated cylindrical defensive spicula of the dermal mem- 

 brane, represented by figure 7, Plate XLIX. It requires great 

 care to obtain these spicula from portions of the dermis by the aid 

 of dissolution of the sponge in boiling nitric acid, but they may be 

 readily seen in situ in a thin slice of the dermis, mounted in Canada 

 balsam, with a power of 600 or 700 linear. This is the only case 

 in which I have found this singular form of spiculum in situ. The 

 one figured represents the normal form in a fully developed condi- 

 tion ; and in such spicula the central canal can frequently be seen. 

 A great number of them are distorted to a very considerable extent ; 

 and some are exceedingly attenuated and have the spines very in- 

 completely developed. 



The spicula of the skeleton are crowded together on the interstitial 

 membranes without the slightest approximation to order. They are 

 very variable in size, some of them being twice the diameter and 

 length of others ; and the ovo-spinulation is equally variable, some 

 of the basal inflations being completely spherical, while others assume 

 every possible variation of the ovoid form . 



This species of sponge is interesting, not only on account of the 

 remarkable development of its oscula and their vital powers of action, 

 but also as affording the type form in situ of the spiculum repre- 

 sented in plate iii. fig. 72, vol. i. ' Monograph of British Sponffiada,' 

 in treating of the anatomy and physiology of the spicula. 



