Simpson — A Revision of the Gorgondlidae. 5 



London, for an excellent sketch of a colony in that museum (fig. 46); to 

 Professor Sydney J. Hickson, Manchester, for kindly sending me portions of 

 the specimens and also the preparations of spicules on whic^h Llie descriptions 

 given in his memoirs are based; Imt most of all to Professor J. Artliur 

 Thomson, who has entrusted the greater part of the new material to me for 

 identification, including the collection of the Indian Museum, Calcutta, the 

 Monaco collection, and the Cape collection referred to a])ove. I cannot 

 sufficiently express my thanks to him for placing his splendid series of 

 Alcyouarian literature at my disposal, for the personal interest he has taken 

 in the work, and for much kindly criticism and aih'ice. 



1 must also thank the Trustees of the Carnegie Trust for a grant towards 

 defraying the cost of illustration, and also the two artists, Mr. George 

 Davidson and Mr. William Smilh, for the trouMe they have taken in 

 preparing the drawings. 



III. Biological Note. 



The Juncellid-group of Gorgonellids are typically shallow-water forms, 

 and occur both in tropical and temperate seas, chieily, however, in tropical 

 waters, but have not so far been found in Arctic or Antarctic seas. They 

 are usually found within the hundred-fathom line, and exist in very shallow 

 water. On the coral reefs of the Mergui Archipelago, numerous colonies may 

 be seen swaying to and fro in the air when uncovered by the water at low 

 tide. This power to survive the heat of the sun in the tropics for as nnich 

 as two hours daily is proof of great vitality in tlic group. 



The colonies may be simple or branched, and when simple may attain to 

 great lengths; specimens of over six feet long are not infrequent. This 

 great length is all the more remarkable wlien it is remembered that there is 

 no jointing of any sort, as is seen in Isis, Mclitodes, and tlie like. They 

 are extremely flexible, sway to and fro in the ocean, and when living nuiy be 

 bent into the form of a figure 8 without the least ciiance of fracture. This 

 is of great morphological significance, and is paralleled in the animal 

 kingdom only Ijy (1) Peiuiatulids e.g. Umbellula}, (2) Antipatliarians, and 

 (3) Nemerteans. 



Nemerteans, however, live a free existence ; Umbellula is also free, and 

 lives embedded in mud at great deptiis. Tiie analogy, tlierefore, restricts 

 itself to Juncellids and Antipatliarians. In the former tlie axis contains 

 lime ; in the latter it is composed entirely of a liorny substance. 



The proportion of coenenchyma to axis is very different, however, in the 

 two cases. In the former the coenenchyma preponderates over tlie axis, but 

 in the latter the reverse holds true. 



