6 THE BRITISH SPONGES. 



turns elastic to its former bulk. From this peculiarity, 

 combined with its pleasant softness, arises the value of 

 sponge ; and for the purposes to which it is applied, in do- 

 mestic economy, and in surgical practice, we are not aware 

 that any other production can be conveniently substituted. 

 When the sponge is recent and living its canals and 

 pores are filled with a glairy colourless fluid like the white 

 of an egg, wMch flows freely out on the removal of the 

 sponge from the water. The quantity of tliis fluid varies 

 according to the species. In some it is copioiis even to 

 nauseousness ; but in the compact Halichondriae there is lit- 

 tle of it, and in the Grantiae it appears to be entirely want- 

 ing. It " has an unctuous feel, emits a fishy odour when 

 biuTit, leaves a thin film or membrane when evaporated, 

 and appears to the naked eye transparent, colourless, and 

 homogeneous, like the colourless part of an egg. But, 

 when a drop of it is examined on a plate of glass under the 

 microscope, it appears entirely composed of very minute, 

 transparent, spherical or ovate granules, like monades, with 

 some moisture. These monade-like bodies, nearly all of 

 the same size and form, resemble the pellucid granules or 

 vesicles, which Trembley has represented as composing the 

 whole texture of the Hydrae, or the soft granular matter 

 we observe in the stems of living Sertularise ; and, indeed, 

 most of the fleshy parts of organized bodies appear to be 

 composed of similar pellucid granular or monade-like bo- 

 dies in different states of aggregation."* — The chemical 

 properties of this fluid have not been ascertained : its sensi- 

 ble qualities, if we assume that the smell of the sponge flows 

 from it, are not altogether the same throughout the class, 



* Grant in Edin. New Phil. Journ. ii. p. 124. 



