AND THE HEBRIDEAN DIAZONA YIOLACEA. 167 



(2) August 12th, on East Sliiant Bank, in the Minch, north-east of Skye, 

 27 fathoms ; some smaller pieces, also pale green. 



Fig. 1 on PI. 13 is reproduced (half-size) from a water-colour sketch of the 

 largest ' Eima ' colony when alive, made by my wife on the yacht, and I 

 give, for comparison, in fig. 2 a copy of the original illustration in Forbes 

 iind Goodsir's paper — both figures showing the green colour of life. 



One of the smaller pieces obtained this summer was preserved in formalin, 

 iind it is still of the same pale transparent green hue as when alive. Another 

 fragment was preserved in alcohol, and it has become of a pale purple or 

 mauve tint, such as is shown in the little rectangle labelled A on PL 13. 

 The largest colony was placed in a tank of methylated spirit and shut up 

 until the end of the cruise. On opening the tank a month later it was found 

 that the spirit was stained a rich green and the Tunicate colony was now of 

 a well-marked violet colour (like the little rectangle B on PL 13), recalling 

 vividly the appearance of Diazona violacea from the Mediterranean. 



There can be no doubt then (as I find Mr. J. Hopkinson adds in a 

 footnote to the Supplement of Alder and Hancock's ' British Tunicata,' vol. iii. 

 p. 100, Pay Society, 1912) that Sijnlethys hebridints, Forb. & Goods., is merely 

 a synonym of Diazona violacea, _^a,Y. The only doubt that remained was as to 

 whether the green Hebridean form could be separated as another species of 

 the same genus, but an examination of the detailed structure of the ascidio- 

 zooid in colonies from both the Mediterranean and the Hebrides has satisfied 

 me that there are no grounds for such a separation. I have now before me 

 the following material in alcohol : — 



Colony from Naples, 1890, colour mauve ; 



Colony from Naples, 1912, colour dull greyish green ; 



Colony from Plymouth (large ascidiozooids), colour mauve ; 



Ditto (basal part, with small ascidiozooids), colour greyish green ; 



Colony from Mull, 1885, colour mauve ; 



Colony from Hebrides (' Runa'), 1912, colour violet ; 

 and although these specimens differ considerably in colour and appearance^ 

 they all agree in structure. The branchial and atrial apertures are, I believe, 

 always G-lobed^ although in contracted or badly preserved specimens it may 

 be difficult to demonstrate the lobes. 1 give (PL 14. figs. 1 & 2) drawings 

 of 6-lobed apertures in both test and mantle from my Hebridean specimen. 

 Then in regard to the structure of the branchial sac every specimen shows 

 n wide range of variation in the number of stigmata in a mesh and in the 

 exact condition of the internal lono-itudinal bars, as I shall show in detail below. 



It is stated in the second volume of ' The British Tunicata ' by Alder and 

 Hancock, edited by Hopkinson (Bay Society, 1906), that Diazona has " the 

 intersections of the meshes papillated " (p. 159) ; and in D. liehridica stout 

 papillse are both figured and described (p. 1G2) and are stated to be a 



