PLATE 1. 



Fig. 1. Diagram of a transverse section through a branch of a colony, show- 

 ing polyps in various stages of retraction. 



Fig. 2. Transverse section of a polyp through the stomodaeum. X 15. 



a, expanded polyp, oral aspect 



a', expanded polyp, seen from the side 



^, expanded polyp with inrolled tentacles 



T, polyp partially retracted 



d, polyp completely retracted 



€, polyp with column retracted, but with expanded tentacles and 



with open mouth 

 7], polyp in longitudinal section 



Fig. 3. Transvei-se section of a polyp just below the stomodaeum. X 15. 

 Fig. 4. Transverse section of a polyp through the lower polvp cavity. 

 X 15. 



