538 ' OLWEN M. REES. 



There are numbers of irregularly shaped spots of a pale yellow colour 

 scattered over the inner surface of the tentacles. Each tentacle from 

 the inner series has two opposite, lateral, irregular patches of white, 

 situated about one-third the length of a tentacle from the base. The 

 purple shade is strongest upon the central area of the inner surface of 

 the tentacle. 



The series of minute spots is described by Gosse and their presence 

 seems to be characteristic of this species. Haddon does not mention 

 their presence in A. gelam. 



Size : diameter of column very variable during life, 6-10 cm. Column 

 15 cm. in height, but probably capable of much greater extension. 

 Diameter of disk about 10 cm. Expanse of tentacular crown about 

 20 cm. Length of larger tentacles 7 cm. Average diameter of pedal 

 disk 7 cm. 



This specimen is about the same size as A. gelam ; the height of the 

 column of the latter being 150 mm. The specimen of A. alfordi collected 

 by Gosse was also fairly large, the height being about 100 mm., it was 

 obtained in the Scilly Isles. 



The specimen from Valentia Island disgorged a partially digested 

 Actinian — probably a Cerianthus ; a number of these were packed with 

 the Aulactinia and were in contact with it. 



Anatomy and Histology : — 



The column wall is thick, the mesogloea being broader in section than 

 the ectoderm ; the latter is deeply folded. The cells of the ectoderm are 

 long and narrow ; they contain numerous granules, which become deeply 

 stained. These granules form a broad zone in the ectoderm. On the 

 outside of the layer is a clear zone, and on the inside near the mesogloea 

 is another narrower zone, which marks the position of the nerve layer. 

 Between these two lie the granules. 



The mesogloea is thick, stains deeply and is homogeneous in structure. 

 The large spaces which are seen in the sections are probably due to the 

 fact that the specimen became very hard before the sections were cut, 

 and this caused the mesogloea to break. 



On its endodermal border the mesogloea shows a delicate fibrous 

 structure, giving rise to a thin plate of circular endodermal muscle. 

 There is no trace of any ectodermal musculature. 



The endoderm is a much narrower layer ; in section it is about half 

 the width of the ectoderm and one-third the width of the mesogloea. 

 The cells of the endoderm do not show such a definite columnar structure 

 as those of the ectoderm, and the cells are not so regularly arranged. 



