Dr. Drummond, who discovered it cast on shore at Larne, in 

 August, 1806 ; — unless, as Dr. Arnott supposes, it be the TJlva 

 rubens of Hudson, a synonyme which I think better referable to 

 JDudresnaia divaricata. 



It is common on many parts of the coasts of England, Scot- 

 land, and Ireland, and is found in the Isle of Jersey by Miss 

 White ; but appears to be, in some districts, less common than 

 M. virescens. This, Mr. Ralfs remarks, is the case about Pen- 

 zance, in Cornwall, and on the Welsh Coast. It is frequent in 

 Torbay, and in other localities of the south of England; and 

 very abundant on the west and south-west coasts of Ireland. In 

 the north-east of Ireland, where it was first noticed, Mr. Thomp- 

 son finds it in profusion, and has observed, among heaps of sea- 

 weed cast on shore " the partiality of the Idotea cestrum, Leach, 

 for the gelatinous Mesogloia vermicularis, plants of which it had 

 very much eaten, leaving the other Algae, of which there were 

 many species in the heap quite untouched." 



I have given the Mediterranean station on the authority of 

 Professor Meneghini, who has received it from Venice and from 

 Trieste. It is omitted by Agardh in his Algae Mediterranean. 



M. vermicularis may be considered the type of the genus 

 Mesogloia, as now defined by J. Agardh, consisting of that por- 

 tion of the older gorius to which I formerly applied the name of 

 TricJwcladia, subsequently changed into Helminthocladia. When 

 I proposed M. multijida of Agardh, as the type of the restricted 

 genus Mesogloia, I was not aware that that species is identical 

 in structure with Nemaleon of Tozzetti. To Nemaleon, M. mul- 

 tijlda is therefore now referred ; M. Iludsoni (of British authors) 

 and M. coccinea to Dudresnaia ; and M. moniliformis, Griff, to 

 Crouania. Respecting the proper place of M. purpurea, Harv. 

 I am at present doubtful. 



Fig. 1. Mesogloia vermicularis, (small specimen): — natural size. 2. Por- 

 tion of the filaments, axial and peripherical, of which the frond is composed. 

 3. Apex, with its spore, and cluster of idtimate fibres : — magnified. 



