ACTINIA FROM THE MERGUI ARCHIPELAGO. 



249 



mous numbers in the endoderm of the upper portion of the body, 

 and but sparsely in the rest of the column. 



Dimensions. Contracted specimen in spirit — height 40 millim . ; 

 diameter of column 22 millim. below, 25 millim. above. Length 

 of tube (in spirit) about 260 millim. 



Hahitat. Deeply burrowiug in mud-flats, low spring-tide, 

 French Bay, King Island, Mergui Archipelago (February 1882). 

 The animal inhabits a thick slimy tube formed by the threads of 

 cast-off cnidae and foreign matter. 



I have received the following memorandum from Dr. An- 

 derson : — 



" The large Actinia I found burrowing in the extensive mud- 

 flats exposed at spring-tides in French Bay, King Island. There 

 was a small depression in the mud around the disk and tentacles, 

 and as they were filled with water, the tentacles were more or 

 less expanded, of considerable size, and prominent. The disk 

 was large, but whether it expanded much beyond the column, or 

 at all, I cannot say. The upper stratum of mud was so soft that 

 I sank halfway up to my knees in it ; but the burrow of the 

 Actinia extended deep below this ; and I consequently expe- 

 rienced considerable difficulty in digging it out. When removed 

 from its burrow, it was very flaccid, but had contracted to about 

 9 inches in length." 



From the foregoing account we may conclude that the fully 

 extended animal measures some 18 inches (460 millim.) in 

 length. It is probable that when fully distended the disk 

 extends beyond the diameter of the column, making it somewhat 

 salver-shaped. As in Cerianthus, the tube is composed of innu- 

 merable cnidas felted together ; entangled amongst these are 

 large numbers of unexploded nematocysts and foreign bodies, 

 such as grains of sand, spicules of sponges and alcyonaria, diatoms, 

 and the hyphae of a fungus. The possession of symbiotic algaB 

 must be very advantageous to this tubicolous actinian ; and it is 

 not surprising that they are mainly massed in the only portion of 

 the animal which is exposed to the light. 



The figures on Plate XIX. sufficiently explain themselves. It 

 must be remembered that the greater portion of the epithelial 

 tissues are lost by maceration. The ectoderm is entirely lost, 

 most of the endoderm has separated from the lower portion of 

 the body and from the mesenteries ; enough, however, is present 



21* 



