PORIFERA 



6 7 



for a time. Later, it comes to rest, attaches itself to 

 some support, and develops into the adult form which is 



d 



h 



FIG. 15. Hypothetical Section of a Sponge: a, superficial layer ; b, inhalant pores; 

 c, ciliated chambers ; d, exhalant aperture, or osculum ; e, deeper substance of the 

 Sponge. 



never capable of locomotion. The fresh-water sponges 

 also multiply by means of gemmules, which are small, 



FIG. 16. Skeleton of a Horny Sponge. 



seedlike bodies to be found in the sponge in the fall. 

 Each consists of a hard coating surrounding a mass of 



