300 GILBERT C. BOURNE. 



circles of tentacles in Actinise do not arise in the manner here 

 suggested is sufficiently proved by the researches of Lacaze 

 Duthiers and the Hertwigs, but I have not seen it contradicted 

 of Fungia that the tentacles are scattered irregularly over the 

 disc. Yet so far is this from being the case,, that on first 

 taking the living animal out of the sea I was immediately 

 struck with the arrangement of the tentacles in definite cycles, 

 rig. 1 is a drawing of F. den tat a, somewhat contracted by 

 spirit, but with the short stumpy tentacles still expanded. 

 Their arrangement will be at once understood by a comparison 

 of the drawing with the diagram (fig. 2). 



Each tentacle is placed, not, as Dana says, on the innermost 

 extremity of each septum, but on a slight elevation of the 

 upper edge of each septum near its innermost extremity ; from 

 the point of attachment of the tentacle the septum is con- 

 tinued obliquely downwards and inwards towards the axial 

 fossa, none but the last two cycles ending at any great dis- 

 tance from it. Since the tentacles correspond exactly in 

 position with the septa, what is stated of the arrangement of 

 the one holds equally good of the other. 



There are twelve primary septa, of which ten reach the 

 mouth, two being rather shorter than the others and placed 

 opposite each end of the long axis of the mouth. The ten- 

 tacles placed on the inner extremities of these septa overhang 

 the mouth, but are small and degenerate. 



Both Lacaze Duthiers (7) and von Koch (21) describe 

 twelve septa as rising simultaneously in the first cycle, making 

 the prime number of septa twelve instead of six. According 

 to the latter six alternate septa grow faster than the others, 

 giving the appearance of two cycles of six each ; this is appa- 

 rently not the case in Fungia whose twelve septa of the first 

 order are, with the exception above mentioned, of equal size. 



There are twelve septa of the second order alternating with 

 those of the first; they reach very nearly to the mouth and are 

 all of equal length ; the tentacles corresponding with them 

 form, with those of the first cycle, a ring surrounding the 

 mouth. 



