166 BRITISH SPONGES: 



that many species of this genus are distinguished by the pos- 

 session of a beautiful branched vascular tissue, which surrounds 

 the fibre, frequently anastomosing and running in every possi- 

 ble direction over its surface. This tissue is not imbedded in 

 the horny mass of the fibre, but is contained in a sheath, which 

 closely embraces it. In some of these vessels Mr Bowerbank 

 observed numerous minute globules, exhibiting every appear- 

 ance of being globules of circulation analogous to those found 

 in the blood of the higher classes of animals. These molecules 

 were extremely minute, varying from the yfi^g-gth to the 

 Jouo 0^^ of an mch in diameter. 



In a recent state the surface of the Spongias appears to be 

 covered with a reticulated membrane of more delicate organi- 

 zation and with finer meshes than the interior network. The 

 interstices of the whole mass is as usual occupied with an orga- 

 nic mucus similar to that of the other genera ;• and in some spe- 

 cies it is not less loaded with minute siliceous spicula than are 

 the fibres themselves. 



The Spongiae are propagated probably by gemmules generat- 

 ed in and from the organic mucus, as Mr Bowerbank has shown 

 in one Australasian species. * 



From their softness and indestructible elasticity, and their re- 

 markable bibulous property, the Spongiae are adapted to many 

 economical uses. These are thus summed up by Ray : — " Spon- 

 giarum multiplex usus est : nimirum 1. ad fomenta ; multo 

 enim diutius decoctoriun quibus membra fovenda sunt calo- 

 rem retinent, quam panni aut linteamina : 2. ad sanguinem ali- 

 umve liquorem imbibendum et exsiccandum, quo Anatomicis, 

 Chinirgis, Mechanicis utiles sunt. 3. Ad ulcera cava, nondum 



* For an account of Mr Bowerbank's discoveries on tlie structure of 

 recent sponges, see tlie Microscopic Journal, i, p. 8 ; and the Annals of 

 Nat. History, va. p. 72. and 129. 



