276 PROF. W. A. HERDMAN ON 



III. DiAZONA YIOLACEA, Sav'igny. 



I have this year been extraordinarilv fortunate in obtaining abundance 

 ■of material of this remarkable species. Previous to my record of last year, 

 I believe only two specimens were known from Hebridean Seas — the one 

 described by Forbes and Goodsir in 1851 as " Si/ntethys hehridicus " and the 

 colony which I noted in 1891 * as having been dredged by the late Duke of 

 Argyll, north of Mull, in 1885. Last year I found one good colony off 

 Barra Head in the Outer Hebrides, and a few small fragments from the 

 East Shiant Bank in the North Minch. This year I dredged over 30 colonies 

 — most of them from a bank in the Inner Sound, north of the Croulin 

 Islands j, iit a depth of about 30 fathoms, but some off the W'est coast of 

 Skye across the mouth of Loch Snlzzort, outside the Ascrib Islands, from 

 30 to 40 fathoms. 



At the Meeting of the British Association at Birmingham last September, 

 I exhibited to the Section of Zoology two large museum jars, the one con- 

 taining several bright violet colonies of Diazona preserved in alcohol, while 

 the other had an equal number of colonies preserved in a solution of formol 

 and still showing distinctly the green colour of the living animal. The 

 contrast in appearance between the two jars was most marked, and was due 

 merely to the method of preservation, all the colonies having been equally 

 green when placed alive in their respective fluids. In the discussion, I was 

 then asked the question — What will be the result if you now put one of the 

 green formol-preserved specimens into alcohol ? I am now able to answer 

 that question as follows : — 



On September 24th I washed one of the colonies from the green jar in 

 running fresh water for a couple of hours, to remove the formol from the 

 surface, and placed it in absolute alcohol at 5.40 p.m. 



Up to 6.0 P.M. no change was visible. 



September 25th, 9.30 a.m., the alcohol was tinged with green and the 

 colony looked paler. 



September 26th — the alcohol was much greener. 



October 2nd — handed the green alcohol over to Dr. A. Holt for chemical 

 examination, and transferred the colony, now of a pale green colour, nearly 

 colourless in places, and of crystalline appearance on the surface, to a jar of 

 new colourless alcohol. 



October 3rd — the alcohol beoinnino- to be green. 



October 4th — fluid still greener ; colony seems colourless on surface. 



November 4th — there has been no further chanoe for some weeks. The 



O 



* Auu. & Mag. Nat. Hist, for August 1891 (ser. 8, vol. vi.), p. 165. 



■1- This is probably the same spot from which Forbes and Goodsir, when on Mr. R. 

 McAndrew's yacht in 1851, dredged the first-described specimen of " Syntethys." 



