OP THE SPONGIADjE. 95 



never to be absent. It even seems to acquire a greater 

 importance in the animal economy as we descend in the 

 scale of beings, until the animal in Jmceba and Actinophrys 

 Sol becomes entirely composed of it ; and in these creatures 

 it seems to perform all those varied functions which in 

 other animals are distributed among a numerous set of 

 especial organs. It thus appears to be the most constant 

 and perhaps the most important attribute of animal life. 

 In its most isolated form, it apparently supersedes every 

 other organ in the animal. In Amoeba it appears to exist 

 in its simplest and most isolated condition, it moves by its 

 contractile power, and absorbs nutriment. In Actinophrys 

 it adds another function to its list of capabilities, that of 

 throwing out pseudo-tentaculse by which it entangles and 

 conveys its prey to its surface. In the foraminated animals 

 it develops further powers, it secretes a chambered shell for 

 the protection of its surface, and throws out pseudo-podia 

 by which it moves over comparatively a considerable space 

 in a short period, and anchors itself at its pleasure in any 

 position or locality it may choose to remain in. As we 

 proceed higher in the scale of creation its functions become 

 more limited, but in the act of digestion it always appears 

 to take a most important part. 



The internal vital powers of the Spongiadse seem to be 

 resident in this substance, which appears to fulfil in these 

 animals all the functions of the nervous systems in the 

 higher classes of creation, gifted with elaborately developed 

 nervous systems, and if we view this extraordinary sub- 

 stance in reference to nervous matter, it seems to lead us 

 irresistibly to the hypothesis that they are to a certain 

 extent identical, or that the latter enters in a difinsed state 

 into the composition of the former. In plants we have 

 movements resulting from irritation closely resembling 

 those arising in animals from nervous action ; but who has 

 ever seen the nerves in plants ? 



In the dermal membrane of sponges we have actions 

 arising from alarm or injury analogous to those induced by 

 nervous influence, but no nervous filaments can be detected. 

 We naturally ask, why does alarm immediately cause the 



