HOW 8P0N0E& GBOW. 



17 



openings Cor the exit of waste matters. Among these 1 

 openings are multitudes of minute openings winch si rve as 

 mouths. These mouths lead by branching canals into little 

 pockets or chambers which are lined with digestive, ciliated 



!i,i 15.— Development <>f a sponpe (Sucoh ciliatum), A. />'. morula seen In seo- 

 tlon; c, segmentation cavity; C, blastula Btage ; /'. eastrula al i i" be- 

 ne stationary, with a few spicules; E, sponge become stationary, wlui 

 Bpicules. Highly magnified. 



cells; the sponge, then, has myriads of mouths and stom- 

 achs (Fig. 14). 



Sponges develop, like all the 

 higher annuals, from true 6gg8. 

 The t'L f L r . after fertilization, 

 begins to grow, and divides into 

 two, four, eight, sixteen, and 

 more spheres, until it looks like a 

 mulberry, which seen in section 

 is as in Fig. 15, . I, /•'. This is the 

 segmentation stage or morula. 

 The cells farther multiply, and 



arrange themselves into a single Fio. 16.— Ciliated embryo or bias- 



11 .1 i 11 tulaofaspo tudra ro- 



ayer, when the embryo is called jj,,,,,,,. (Highly magnified.) 



a blastula. Some of the cells are 



ciliated, and as a blastula the embryo leaves the parent 



sponge and swims about in the sea (Fig. Id and Fig. 15, ( ). 



