Developmental Problems 

 in Cam^anularid 



Sears Crowell" 



Departtiient of Zoology, Indiana University, Blooiningtun, Indiana 



This report reviews a limited number of experimental studies 

 on the thecate or calyptoblastic colonial hydroid Campanularia 

 flexuosa (Hincks). The selection of topics has been biased by the 

 fact that most studies of developmental problems in hydroids have 

 employed either hydra or athecate (gymnoblastic) species (e.g. 

 Cordylophora, Corymorpha, Hydractinia, Tuhularia). This report 

 1 think, can be most useful if emphasis is placed upon the peculiar 

 features of thecate forms and on differences between the two groups. 

 No attempt has been made to cover comprehensively the morpho- 

 genesis of thecate hydroids or related work of other investiga- 

 tors. I have tried to point out a few of the interesting unsolved 

 problems 



The principal topics are: 



1. Patterns of colonial growth 



2. Alterations of the pattern of growth 



3. Aging 



4. Regression and replacement of hydranths 



5. Reconstitution studies 



6. Hvdranth differentition 



iThe research lias been supported by a research grant (H-1948) from the National 

 Heart Institute, U.S.P.H.S., and by a grant-in-aid from the American Cancer Society. 



^Department of Zoology, Indiana University, Bloomington, Indiana and the Marine 

 Biological Laboratory, Woods Hole, Mass. Contribution No. 707 from the Depart- 

 ment of Zoology, Indiana University. 



297 



