PORIFERA 



99 



Type of phylum, Grantia ciliata (living) (Fig. 36). 



This is a hollow cylinder, somewhat spindle-shaped, about 

 half an inch high by a quarter of an inch wide, attached at base 

 to some solid object. It is dull yellow to gray in color, with a 

 large opening edged with spicules at its summit. It is found 



'0^ 



Fig. 36. — The common sponge, Grantia ciliata. The protecting and supporting 

 spicules are calcareous. A, longitudinal section (X lo). B, transverse section 

 ( X 250). b., bud ; e., eggs ; eti., endoderm lining the flagellate canals, each armed 

 with a single long cilium ; ex.c, excurrent canals; /., "flesh" of sponge; fl.c, 

 flagellate canals; in.c, incurrent canals; mes., mesogloea, with scattered nuclei; 

 0., osculum; os., ostia, tlielniteFope'nings of the incurrent canals; o.sp., the very 

 long spicules surrounding the osculum ; p.c, paragastric cavity ; sp., the long 

 spicules surrounding the ostia; sp'.\ the three-rayed spicules surrounding the 

 flagellate canals; sp.c, paragastric cavity shown in longitudinal section. (After 

 Brooks, relettered.)" 



growing in tide pools from Rhode Island to Greenland and on 

 the northern coasts of Europe. 



The body wall consists primarily of three cell-layers, ectoderm, 

 endoderm and mesogloea. It is protected and a firmness given 



