OBELIA 73 



cleavage, occurs as in Hydra. The result of the first stages in de- 

 velopment is the formation of a tiny, ciliated larva, known as the 

 planula. The planula swims around for a time, then becomes 

 attached to some suitable solid material in the water and soon 

 begins to change its form and to develop into the attached, colonial 

 asexual phase of Obelia with which we began the study of the life 

 history. (W. f. 37.) 



TEXTBOOK REFERENCES 

 Woodruff, pp. 71-78. 



Curtis and Guthrie, pp. 274-281. 

 Guyer, pp. 204-206 ; 667-669. 

 Hegner, pp. 112-138. 

 Newman, pp. 176-178. 

 Shull, pp. 85 ; 159-163. 



GENERAL REFERENCES 



Hickson. " Coelenterata and Ctenophora," in the Cambridge Natural His- 

 tory (Macmillan). 

 Hickson. An Introduction to the Study of Recent Corals (Longmans). 

 Parker and Haswell. Textbook of Zoology (Macmillan). 



