244 The Irish Naturalist [Sept., 



The hydranth of the American Rhizogeton is about 3-6 mm. in length, 

 with about 12 tentacles. The perisarc extends nearly to the base of the 

 tentacles. The colony is of an orange colour. The hydranth of the 

 Valencia specimens is, therefore shorter, but carries more tentacles 

 It shows also a difference in colour. 



Tubularia Indlvlsa (Linn.) 



Colonies taken in Doulus cave by the Misses Delap, May, 1897. 

 Actinulae visible inside the gonophores. 



Tubularia larynx (Ellis and Solander.) 



One of the commonest Hydroids in the harbour, where it lives attached 



to the bottom of boats. Anchored in the harbour were two large old 



hulks used for storingice, and during our visit they werebeached for repairs, 



and also a smaller hulk used for storing coals. The bottoms of these 



hulks were completely covered with barnacles, ascidians, and Tubularia 



larynx. A large number of nudibranchs, chiefly Dendronotus arborescens 



and Eolis lineata^ were feeding upon Tubularia and they partly accounted 



for the great masses of old stalks, as the number of hydranths in each 



cluster was small compared with the number of headless stalks. The 



clusters of Tubularia, often four to five inches in height, were not formed 



by the growth of a single colony, but by a succession of colonies. The 



young actinulae settling down upon the stems of the old colonies, which 



had died away or been eaten by the numerous nudibranchs. In some 



places on the hulks the old stems only remained, forming a thick matted 



mass upon which polyzoa were growing. Tubularia larynx was only 



found on the bottom of the hulks, small boats, and buoys, which had 



been some time in the harbour. It was not seen upon the shore between 



tide marks, nor dredged. A small boat which had for some time been 



at the bottom of the harbour in a few fathoms of water was recovered 



and beached during our visit, I examined the boat soon after it was 



hauled ashore and found it completely and solely covered with thousands 



of specimens of L'epas Hillii. Not a single Hydroid was seen ; even Ascidiella 



aspersa, common in the harbour and on the bottom of the hulks, was also 



absent. 



Although this species was confined to the bottom of boats and other 

 floating objects, yet the shape of the colonies showed considerable 

 variation, extending from a close, compact colony with stems less than 

 an inch in len;^th, to straggling colonies from three to four inches in 

 length. 



In some of the colonies the stems are straight and slender, in others 

 greatly contorted and twisted. The stems are only branched close to 

 the base, and vary in thickness in the different colonies. The annulation 

 of the stems is also very variable, in some colonies quite smooth, except 

 at the base, in others the annulations occur at irregular intervals. 



The stems in some of the specimens have the appearance of being 

 branched at intervals, but a close examination shows that the branch 

 formation is due to the attachment of the actinulae liberated from the 



