224 LIVEEPOOL BIOLOGICAL SOCIETY. 



and sanidasters (not spirasters, as I called them in my 

 previous report) 0'012 to 0"016 mm. in length, and are 

 both very typical forms. The oxyasters are found only in 

 the choanosome, the sanidasters chiefly in the ectosome, 

 and a few also in the choanosome. 



Besides those megascleres and microscleres, I found 

 fragments of a third kind of spicule (see fig. 2 c, PL VII., 

 Vol. III.), the appearance of which, in my former report, I 

 compared with broken blades of fret saws. The largest of 

 these pieces measured 0*08 by 0'0014 mm. They were 

 found just beneath the surface of the sponge. But now I 

 think it quite possible that they do not belong to Seiriola 

 at all, but rather to Stelletta colling si, in which latter sponge 

 I now describe them for the first time (see PI. XIV., 

 figs. 1 and 2). As my specimens of Seiriola and Stelletta 

 had been taken from the same rock, and had been kept 

 together for some time in the same jar of spirits, it is pos- 

 sible that fragments of those spicules found their way acci- 

 dentally into the Seiriola. 



Oscula and pores could not be distinctly seen, neither 

 in the living specimens nor in sections. The incurrent 

 and excurrent canals seem to branch in a very irregular 

 manner through the sponge. The chamber-system ap- 

 pears to belong to the eurypylous type,* in so far as the 

 flagellated chambers lie closely round the excurrent canals, 

 and as the apopyles are not continued into special tubes 

 and are extremely short. At the same time the term 

 "eurypylous" does not apply correctly to /SW/v'o/a, as the 

 apopyles are extremely narrow. The flagellated chambers 

 and collar cells are very small. The former are oval, and 

 measure 0*012 by O'OOS mm. The collar cells measure 

 0-0013 mm. 



The mesoderm of Seiriola consists of sarcenchym, the 

 * Sollas, loe. cit., p. xv. 



