BRITISH SPONGIAD^E. 283 



varying in diameter from once to five times that of the 

 larger spicula, and from the granulated appearance of their 

 contents, they have every appearance of being reproductive 

 organs. These bodies are not readily to be detected in the 

 sarcode, either in the living or the dead state, and they 

 require the treatment with acid to liberate them from the 

 surrounding sarcode. The structure of the skeleton is very 

 fragile, and the number of spicula in its reticulations is 

 very small. A full-sized spiculum measured ^th inch in 

 length. 



7. Isodictya elegans, Bowerbank. 



Sponge. Sessile, parasitical ; embracing the stems of Fuci 

 or Zoophytes ; branches cylindrical, fistulous. Sur- 

 face smooth. Oscula simple, terminal, or slightly 

 elevated. Pores inconspicuous. Dermal membrane 

 furnished with a reticulation of single spicula, areas 

 usually triangular, rarely quadrangular. Skeleton : 

 primary and secondary lines unispiculous, very regu- 

 lar, slender, and delicate ; spicula sub-fusiformi acerate, 

 short, and stout. Interstitial membranes. Tension 

 spicula acerate, slender. 



Colour. Fawn-yellow, in the dried state. 

 Habitat. Island of Herm, Rev. A. M. Norman. 

 Examined. In the dried state. 



The specimen which is the type of this species is unfor- 

 tunately broken into four pieces, of nearly an equal size, 

 varying from an inch and a half to nearly two inches in 

 length ; when whole it would have closely resembled in 

 form and appearance one of the lattice-formed species of 

 Chalina. The branches are all more or less cylindrical, and 

 some attain a diameter of nearly half an inch ; each con- 

 tains a small thread-like branch of the Fucus on which it is 

 based, and it also has an excurrent canal extending nearly 

 the whole of its length, which terminates in an open mouth 



