PORIFERA 

 Self-Testing Exercise 



223 



Protozoa are (1) composed of one (2). Examples 



are the amoeba, which (3) by changing its body form and 



the Paramecium, which moves by means of (4), tiny threads 



of (5) . These one-celled animals carry on all the (6) 



of higher animals, including (7) . 



PROBLEM II. WHAT ARE THE CHARACTERISTICS OF SOME 

 SIMPLER INVERTEBRATES? 



Porifera (Lat. porus, pore ; ferre, bear) or sponges. The body 

 of a sponge contains many pores through which water bearing food 

 particles enters. They are classified according to the skeletons 

 they possess into limy, glasslike, and horny fiber sponges. The 

 last named are the sponges of commerce. Most sponges live in 

 salt water ; they are never free swimming. There are about 2500 

 known species. 



Calcccrecc 



Demispongia 



wantux 



Venuss- flave: 



bath. Sponge 



The following is the classification of Porifera : — 



Class I. Calca'rea, having limy spicules in the body. The Grantia seen along our northeastern 

 coast is an example. 



Class II. Hexactinel'lida. Sponges having glasslike spicules, arranged on three axes. Exam- 

 ple, Venus's flower basket. 



Class III. Demospon'giae. Sponges with glasslike spicules, not arranged on three axes, or 

 with skeleton of horny fiber, the latter type represented by the bath sponge. 



The structure of a sponge. The simplest kind of sponge is hi 

 the shape of an urn, attached at the lower end. Cut lengthwise, 

 such an animal is seen to be hollow, its body wall pierced with 

 many tiny pores or holes. These pores open into a central cavity, 

 which in turn opens by a large hole, called the osculum (os'ku-lwm) 

 or mouth, into the surrounding water. 



