96 ANATOMY AND PHYSIOLOGY 



closing of the pores in Spongitta, and suspend inhalation 

 and imbibition? What unknown cause is it that effects 

 these actions usually dependent on the exertion of nervous 

 energy ? In the opening and closing of the defensive cones 

 of spicnla in Grantia ciliata we have a resemblance of 

 muscular action, without the presence of muscles ; but here 

 we have a sufficient cause for the effect in the active vibra- 

 tion of the cilia inducing a flow of water which produces 

 the same results that might otherwise have ensued from 

 muscular action, but we have no such solution to the 

 inherent powers of action in the sarcodous membranes of 

 the Spongiadse, or in sarcode in its purest and most iso- 

 lated forms. Whence then comes the power that inspires 

 the action of the cilia in the sponges, if it be not from the 

 sarcode in which their bases, or the cell whence they ema- 

 nate, are embedded ? If the cilia be removed from the 

 animal, enveloped in their surrounding sarcode, their action 

 is continued vividly for a considerable period, but if a 

 single cilium be accidentally separated from the mass, its 

 vibratory motion is almost immediately extinguished ; it 

 has been separated from the vital influence that endowed it 

 with action. 



But let us return again to the dermal membrane of the 

 Spongiadae, and its internal lining of sarcode, what 

 inherent power then is it that renders this wonderfully 

 plastic tissue so sensitive and self-acting. Is sarcode 

 another form of nervous matter? Or is that vital prin- 

 ciple infused in sarcode ? That it contains an inherent 

 vitality independent of its connexion with other parts of the 

 animal, is distinctly proved by its pure existence in Acti- 

 noplirys Sol, and by its independent action and movements 

 when portions of it are removed from SponyiUa, or from 

 some of the marine Spongiadse. If this supposition be 

 true, then the whole of the phenomena of its existence in 

 Actinoplinjs Sol, in the Spongiadas and in every other form 

 is at once explained. Why should we not have nervous 

 matter without tubular structure surrounding it ? If this 

 hypothesis, that sarcode is a diffused form of nervous 

 matter, or that it exists in a diffused form in sarcode, be 



