ERNEST WARREN. 



to project down into the mouth and we should have the 

 stomodasum of the Anthozoa. 



Development of the Hydranth. — The growing point of 

 the hydrorhiza gives off outgrowths which develop into short 

 hydrocaulus-branches bearing a single, terminal hydranth. 

 The branch, or hydranth-pedicel, and the hydranth grow up 

 together, the hydranth being marked out almost from the 

 first by a slight terminal swelling to the outgrowth (text-fig. 1; 



Text-pig. 2. 



Bimeria rigida.sp. n. A. Young hydranth with first-formed 

 tentacles. b. Hydranth showing the formation of a second 

 series of tentacles, c. Older hydranth with a third series of 

 tentacles. X 40. 



PI. I, fig. 1). The distal surface becomes flattened, and this 

 will form the oral surface. There is a tendency for the columnar 

 ectoderm cells of this flat surface to slope towards the centre 

 even at this young stage, but the condition becomes more 

 marked in the later stages. The whole structure, including 

 both the young hydranth and the young pedicel, is covered 

 by a uniform, thin and apparently soft layer of perisarc. 



Around the border of the oral surface some five or six 

 blunt outgrowths arise ; these are the beginnings of the 

 tentacles (text-fig, 2, a). They appear capitate even at this 

 early condition. The ectoderm cells in the middle of the 

 oral surface become deeper, and ultimately a horizontal split 



