FIRST LESSONS IN ZOOLOGY 



Upon cutting a dry sponge in half there are to be seen large 

 canals which have large openings called oscula; these are 

 really openings for the exit of waste matters. Among these 

 large openings are multitudes of minute openings which 

 serve as mouths. These mouths lead by branching canals 



1 



17. Pheronema Annne, half natural size, with stellate and anchor -like 

 spicules, much enlarged. 



into little pockets or chambers which are lined with diges- 

 tive, ciliated cells; the sponge, then, has myriads of mouths 

 and stomachs (Fig. 18). 



Sponges develop, like all the higher animals, from true 

 eggs. The egg, after fertilization,, begins to grow, and di- 



