DUSEIDEIA. 191 



By a longitudinal section of it, we discover that the sponge is 

 tubular and empty in its lower half, but the upper is more or 

 less filled with a confused granular mass adherent to the sides . 

 and by a section in the contrary direction, a regular, though ob- 

 scure, circle of cells may be detected, in each of which there 

 seems to be a small white globular egg or oviform body. From 

 this structure I am led to believe that the D. papillosa is really 

 the nidus of some invertebrated animal, probably of a species of 

 Natica. WTiatever it may be, it is found sometimes as a single 

 mammiform process, but commonly it is gregarious, and the va- 

 rious processes may be united together by a thin crust, of the 

 same texture and composition, spreading over the shell on 

 which the sponge is parasitical. Thus, in the specimen from Mr 

 Bean here figured (Fig. 18.) the crust has so buried and veil- 

 ed the shell that its species is not recognizable. 



The figure w'hich Montagu has given of his Spongia Icevi- 

 gata might lead to the conjecture that it and D. papillosa v^ere 

 the same thing, but the descriptions wdll by no means tally. 



Duseideia papillosa is nearly allied to the Alcyonimn ocella- 

 tum of Ellis and Solander, Zooph. p. 180, tab. i. fig. 6 ; and it 

 is probable that the two productions are of the same nature, 

 whatever this may be. 



Fig. 18. 



Duseideia papillosa. 



