MARINE BIOLOGICAL STATION AT PORT ERIN. 33 



suspension of the circulation in one or more tanks owing 

 to the growth, in the supply pipes, of living organisms, 

 notably the tube-building Polychsete worm Sahella 

 pavonia and the compound Tunicate Botryllus smaragdus. 

 A large specimen of the former, inhabiting a tube nine 

 inches long, was found obstructing the now on one 

 occasion, and a colony of the latter was in the same way 

 responsible for the death of half-a-dozen sea bream. It 

 is worthy of note that the colour in the case of both these 

 organisms was not affected by the absolute darkness in 

 which they had lived for so long a time. I examined 

 both closely, and was not able to appreciate any difference 

 between them and others of the same species living in the 

 light. 



Amongst the organisms which have appeared spon- 

 taneously in the tanks is a colony of the Monaxonid 

 sponge Halichondria panicea, which has gradually 

 attained large dimensions since I first noticed it quite 

 early in the year. It is gradually extending itself over 

 the back wall of the tank, and now measures about 16 

 inches by 8 inches. In addition to the Hydroid first 

 noticed on the carapace of the spiny lobsters living in 

 the tanks, and which is now being described by Miss 

 Thornely, we have had extensive colonies of another 

 species, Podocoryne carnea, living upon the gravel at the 

 bottom of several of the tanks, and we were able to watch 

 the liberation of the medusae. Multitudes of another 

 medusa, identified by Mr. E. T. Browne as probably young 

 Sarsia tuhylosa, were seen in several of the tanks, as well 

 as in the spawning pond in the spring and early 

 summer, and I am inclined to think that the parent 

 Hydroid, a species of, Syncoryne, is growing in quantity 

 in the suction pipe through which the supply of water 

 from the sea is drawn. 



