THE GRANTIA ^ 



Phylum Porifera Class Calcarea 



Exercise 1. — Occurrence and External Features. 



(a) Scypha coronata (Grantia sp.) is a sponge commonly found 

 attached to wharf-piles or other objects just below the low-tide mark. 

 If living specimens are available, add powdered carmine to the water 

 containing them and determine the direction of water currents through 

 the individual sponge. 



(b) Examine in separate watch glasses a dried specimen of Scypha 

 and one preserved in fluid. Observe the shape, region of attachment, 

 and the large excurrent opening, the osculum (c/. Fig. 41). The many 

 small openings on the surface are called ostia. Minute spicules project 

 from the surface; note their arrangement about the osculum. Speci- 

 mens with one or more buds should be examined as demonstrations, if 

 not observed in your own or in a neighboring specimen. Draw one of 

 your specimens ( X 4) to show external features. 



Exercise 2. — General Internal Structure. 



(c) With a sharp scalpel or a razor blade make longitudinal and 

 cross sections of the dried specimen. The large central cavity from 

 which the osculum opens is called the cloaca. The many small open- 

 ings into the cloaca, called apopyles, lead from the excurrent canals 

 which lie radially in the wall of the sponge. The ostia, previously 

 observed upon the external surface, can be seen opening into the 

 incurrent canals which also lie radially in the wall of the sponge. 

 The minute openings which lead from the incurrent into the excurrent 

 canals can be seen only in prepared sections. Draw (X 10) a por- 

 tion of the wall to show the features observed. Indicate by arrows 

 the course of water through the canal system. 



1 According to Libbie H. Hyman, Science, May 7, 1937, p. 454, the Woods 

 Hole Grantia should be called Scypha coronata (Ellis and Solander) 1786, syn. 

 Spongia coronata (Ellis and Solander). The word "grantia" has become so 

 familiar to American zoologists that its use, as the common name to designate 

 this type of sponge, still seems justifiable. 



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