94 



COLLEGE ZOOLOGY 



Osculum 



Figure 46. Above, a simple ascon type of sponge 

 (Leucosolenia) . A small colony. Right, a young 

 sponge of the ascon type. Highly magnified. The 

 arrows indicate the course of water into and out of 

 the sponge. 



nal surfaces. It is always much eroded with 

 chambers and canals of various sizes con- 

 nected to the exterior by pores and oscula. 

 The mesoglea is often so fluid that a strong 

 oscular current throws up transparent chim- 

 neys from it which are maintained erect by 

 the forces of the current alone. 



The central cavity is lined by a single 

 layer of collar cells (Fig. 47); these choano- 

 cytes are in loose contact with one another 

 and resemble the cells of the flagellated 

 protozoans (Fig. 21). The flagella of these 

 collar cells beat constantly, creating a cur- 

 rent of water. 



If a little coloring matter is placed in the 

 water, it will be drawn into the animal 

 through minute incurrent pores in the body 

 wall and pass out through the osculum, 

 which is therefore an exhalent opening and 



Spicule 



Pore 



not a mouth. Sponges are the only animals 

 in which the large opening is limited to an 

 outward current of water. 



SCYPHA-A SYCON SPONGE 



Morphology 



Scypha appears to be the correct generic 

 name of the sponge that occurs along our 

 eastern coast which was formerly called 

 Grantia* It is a comparatively simple marine 

 type of sponge, permanently attached by one 

 end to rocks and other solid objects. It varies 

 in length from Vi inch to almost an inch and 



* Grantia has been recorded three times from the 

 Gulf of St. Lawrence and is abundant in Europe, 

 but as yet has not been reported for the United 

 States. 



