GRANTIA. 15 



GRANTIA. 



This form is quite common along the New England coast, 

 where it occurs attached to rocks, seaweeds, and submerged 

 woodwork from just below the lowest tide-mark to a number of 

 fathoms in depth. You should visit an old wharf where speci- 

 mens may be found, and study their relation to the forms with 

 which they are associated. Specimens will be found to vary 

 considerably in size. The largest sometimes reach an inch in 

 length. 



1. Examine a dry specimen and notice its general shape, 

 manner of attachment, and osculum. The osculum is surrounded 

 by a funnel of rather long spicules. Distributed over the gen- 

 eral surface, more or less hidden by the numerous spicules, are 

 many small pores. Their presence may be demonstrated more 

 satisfactorily later. 



2. Look for indications of budding. If your specimen does 

 not show this, examine others. 



Make an enlarged drawing of a sponge. 



With a razor or sharp scalpel cut a dry specimen into halves, 

 with a stroke from base to osculum, and notice: 



3. The central cavity or cloaca. 



4. Many apopyles, the inner openings of tubes that are em- 

 bedded in the walls of the sponge, will be seen opening into 

 the cloaca. Are the apopyles arranged in any order? 



5. With the low power of your microscope (with the light 

 turned off) examine the cut wall and find that it is traversed by 

 parallel tubes. Determine that these tubes are of two kinds. 



(a) Regular, nearly cylindrical tubes that open into the 

 cloaca through the apopyles and that bear tufts of spicules on 

 their closed ends, at the surface of the body. These are the 

 radial canals. It is frequently hard to see their openings into 

 the cloaca, as the apopyles are narrow, so the section only occa- 

 sionally passes through them. 



(6) Smaller and less regular tubes that open on the outer 

 surface between the clusters of spicules, and do not open into 



