mi; PORIFERA. 



I 



111 



FIG. 12. A. Hypothetical section of a SpongWa: a. superficial layer; 6. fnhalent 

 apertures; c, ciliated chambers ; d, an oxhalcnt aperture ; f, deeper MI h stance 

 orthe sMonire. The urnnvs indicate the direction of the currents. B. A email s 

 oMa with :v sincjle exhalent aperture, seen 1'rom above (after Lieberkflhn): n. in- 

 halent apertures ; c, ciliated chambers ; d. exhalent aperture. C. A ciliated 

 chamber. D. A free-swimming ciliated embryo. 



