163 



[WORK FROM PORT ERIN BIOLOGICAL STATION.] 



Note upon the yellow variety of Sarcodictyon catenata, 

 Forbes, with remarks upon the Genus and its species. 



By W. A. Hekdman, D.Sc., F.K.S., 



PROFESSOR OF NATURAL HISTORY IN UNIVERSITY COLLEGE, LIVERPOOL. 



[Read December 14tli, 1894.] 



Plate VITI. 



In 1883, I published a somewhat detailed account* of the 

 structure of the ordinary form of Sarcodictyon catenata, 

 Forbes, from the examination of specimens dredged at 

 Lamlash and in Loch Fyne, on the West Coast of Scot- 

 land, in 1880 and following summers. Some of my 

 colonies from Loch Fyne were of a pale yellow colour, 

 and an investigation of these showed that they only 

 differed from the red colonies in having the numerous 

 calcareous spicules of the mesogloea perfectly colourless 

 in place of being of a dull red tint. Hence, I came to the 

 conclusion that here, just as in Alcyonium digitatum, 

 where several distinct colours of colony are found, the red 

 and the pale yellow colonies were merely cases of colour 

 variation, and that all the specimens that I had examined 

 were to be referred to the one species, Sarcodictyon 

 catenata. Moreover, I made the suggestion that probably 

 Forbes' second species, S. agglomerata, which was saidf 

 to differ from S. catenata in being of an " ochraceous 

 yellow " colour, and in having the polypes placed in little 

 groups of from three to five instead of in single file, 

 would prove to be the same species, since (1) several of 

 my red colonies had the polypes in groups, and (2) the 

 yellow colonies bridged the gap as regards colour. 



* Proc. R. Physical Soc. Edinburgh, vol. viii., p. 31. 

 t Trans. Roy. Soc. Edinburgh, vol. xx., p. 307, 1851. 



