18/2.] DR. J. S. BOWERBANK ON THE SPONGIADiE. 115 



February 6", 1872. 



R. Hudson, Esq., F.R.S., V.P., in the Chair. 



The following papers were read : — 



1. Contributions to a General History of the Spongiache. 

 By J. S. Bowerbank, LL.D., F.R.S., &c.— Part I. 



[Received January 15, 1872.] 

 (Plates V. & VI.) 



Genus Tethea. 



Tethea is eminently a natural genus ; the generic characters are 

 well maintained in all the species with which I am accpiaiuted. 

 There is always the same radiation of skeleton- fasciculi from the 

 base or centre of the sponge ; and this radiation is rarely in a straight 

 direction, but almost always in lines more or less curved, giving a 

 greater amount of resistance to any attempt to rend the substance of 

 the animal asunder. Their defences against the attacks of smaller 

 enemies are also beautifully apparent and exceedingly varied, so as 

 to enable us to discriminate species with certainty by the combina- 

 tions of the various forms of their spicula, which are evidently de- 

 signed by nature to offer a passive resistance to every class of enemies 

 to which they may be exposed. Thus the powerful primary defen- 

 sive spicula of the surface, bristling at every part to meet the attacks 

 of their larger assailants, render them any thing rather than an agree- 

 able prey to any fish disposed to make a meal off them. When the 

 larger external defensive spicula are not present, their places are 

 usually supplied by an abundance of large and strong sphero-stellate 

 spicula with sharp and powerful radii, as in T. Ingalli and in our 

 British species T. lyncurium. The innumerable small but acutely 

 pointed stellate spicula usually imbedded in the dermis and scattered 

 over the surfaces of the interstitial membranes provide in an especial 

 manner against the attacks, both externally and internally, of the 

 small annulate and other creatures that would otherwise be prone to 

 feast on their membranes and sarcode. The beauty and complete- 

 ness of these conservative contrivances of nature for the preservation 

 of these inert and humble creatures are wonderfully illustrative of 

 the wisdom and beauty of creation. 



Tethea mtjricata, Bowerbank. 



Sponge spherical, subconical, sessile ; surface even, minutely 

 hispid. Oscula terminal. Pores congregated ; porous areas ex- 

 ceedingly numerous. Dermis thin, abundantly furnished with stout 

 elongo-attenuato-stellate spicula. Connecting spicula attenuato- 

 expaudo-ternate-simple and bifurcated, very large and long, nume- 

 rous ; also recurvo-ternate, long and slender, and, rarely, spiculated 



