CHAPTER IX 



SPONGES, FLAT WORMS, AND ROUND WORMS l 



i. SPONGES GRANTIA 

 (Grantia ciliata Fiem.) 



Grantia (Fig. 69) is a simple sponge in- 

 habiting the salt water along the coast of the 

 New England states just below the low-tide 

 mark.. Here it is found attached by one end 

 to rocks and other solid objects. Unlike 

 Hydra, Grantia is permanently attached, 

 never moving from place to place as an adult. 

 Its distribution in space is effected during 

 the early embryonic stages, at which time 

 cilia are present, enabling it to swim about. 

 Grantia varies in length from one half an 

 inch to almost an inch, and resembles in 

 shape a slender vase that bulges slightly 

 FIG. 69. A simple near ^ e cen ter. The distal end of the 

 sponge. (After animal opens to the exterior by a large ex- 

 Minchin in Lan- current pore, the osculum. This opening is 

 surrounded on all sides by a circlet of long 

 straight needles called spicules. Smaller 

 spicules protrude from other parts of the body, giving the 



kester's 

 tise.) 



Trea- 



1 Since it was impossible to include in this book detailed discussions of 

 types from every phylum of the animal kingdom, many groups are not rep- 

 resented. In this chapter three animals are briefly described in order that 

 the step from a simple Ccelenterate, like Hydra, to a complex Annelid, like 

 the earthworm, may not be too abrupt. The sponges, flat worms, and 

 round worms possess certain organs that help the student to understand the 

 structure and functions of similar organs in more complex animals. 



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