8 



BRANCH PORIFERA. 



BRANCH PORIFERA 



THE SPONGES. 



SPONGES during life are quite different from the 

 mere sponge-skeleton which is the article of commerce. 

 They are more or less gelatinous (je lat'i nus) masses, 

 found mostly in salt-water, and are supported by a frame- 

 work which may be either calcareous, silicious, or horny. 

 The forms of sponges are of great variety. 



FIG. 12. 



FIG. 13. 



CLASS SPONG-IA (spun'ji a). 

 ORDER CALCISPONGIA (kal si spun'ji a). 



A Calcareous Sponge, G-rantia (gran'ti a), of about half 

 an inch in height, 

 well illustrates 

 the anatomy of 

 the Branch. Wa- 

 ter is induced to 

 enter, through ex- 

 ternal pores (Fig. 

 12), to small ni- 

 di ate chambers 

 which are lined D 

 with collared fla- 

 A gellate cells. 



7i 



a cil i n'ta. 

 Calcareous Sponge. 



c, 



Internal Anatomy of Grantia. 



These flagella liot B, "cross - section, " diagrammatic. 



Crown of spines around 



excurrent opening. P, only whip along 



Pores admitting water, " 



as indicated by arrows, the Water, but, 



If, Root -like base. 



(About twice the natural like CodoSlgaS, 



size.) . ,, 



seize upon all nu- 

 tritive matter which the water con- 



showing that the "pores" lead 

 into converging tubes (C") which 

 open internally into a central cav- 

 ity ( C'c). S, Spicules arranged as 

 strainers over "pores." C, More 

 enlarged view of "tube," show- 

 ing it to be lined with Codosiga- 

 like cells. D, A few of the cells 

 highly magnified. 



