12 



SPONGES. 



FIG. ii. Ascetta primordialis, I. 0, exhalent opening ;/, inhalent pores ; 

 -, ova. Star-like spicules are seen on the outside. II. Section showing 

 pores (/), with cilia of the cells extending into them. III. Cell show- 

 ing lash, or cilium. IV. Same, with lash retracted. V. Embryo f As- 

 cetta mirabilis. VI. Section of embryo. 



