140 BRITISH SPONGES: 



and Belfast, Win. Thompson. Dublin bay, A. H. Has- 

 sal. 



" This spong-e is of a corky nature, resembling the close tex- 

 ture of the stalk of some species of Boletus. It has rarely any 

 other pores than what are formed by the fibres, which are so 

 extremely fine as not to be visible to the naked eye, even when 

 broken ; and with the assistance of a pocket lens, they are not 

 definable on the surface. Its colour is orange-yellow when 

 fresh, becoming brown when dry : its shape is indefinite, but it 

 has the singular property of being attached only (so far as I 

 have been able to ascertain) to old univalve shells, which it en- 

 tirely invests. It is also remarkable, that few instances occur, 

 where the hermit-crab has not formed a lodgement in the nu- 

 cleus shell, and there appears to be a great struggle between the 

 two parasitical intruders, as the sponge is continually endea- 

 vouring to fill up the aperture of the shell, while the crab, by 

 its occasional motion in search of prey, frustrates that natural 

 propensity of the sponge. Notwithstanding the efi'orts of so ac- 

 tive and restless an intruder, the gradual and insensible increase 

 of the sponge gains upon the premises of the crab ; it pushes it 

 on all sides, and completely lines the interior surface of the 

 shell, so that the crab soon finds its habitation too small, and is 

 compelled to search for a more capacious home. 



" The species of shell may frequently be traced which con- 

 stitute the nucleus of this sponge. Buccinum reticulatum and 

 imdatum, Turbo terebra and littoreus, are frequently covered 

 by this sponge, except more or less opening to the aperture of 

 the shell. 



" It is a curious circiunstance that no instance has occurred 

 where this sponge has been attached to a living shell, or such 

 as were inhabited by its proper animal. Either the increase of 

 the sponge must be very rapid, or its efibrts to inclose the aper- 

 ture of the shell, must be most successfully perforaied between 



