Rev. M. J. Berkeley on Fucus Labillardierii. 57 



latter and Obisium. There is one point of importance which yet 

 remains to be ascertained, and the more so from its having been 

 taken as a primary character in the classification of the Arach- 

 nida, — the means by which the above animals respire. Trevira- 

 nus has described two rows of puncta as occurring both upon the 

 upper and under segments of the abdomen in ChelifeVj which he 

 regards as stigmata, but states also that he was unable to detect 

 either tracheae or pulmonary sacs in their situation. It is most 

 probable therefore that they were merely impressed points, serving, 

 as in others of the class, for the attachment of muscles. Be 

 that as it may, I have been unable to discover any indications of 

 such external openings in Obisium, or to arrive for the present at 

 any satisfactory conclusion in regard to the existence of an in- 

 ternal respiratory apparatus ; but I introduce these remarks here 

 for the purpose of inquiring whether, if we knew the precise con- 

 ditions under which the breathing of these animals was effected, 

 it is then a function of sufficient value to be adopted in the ar- 

 rangement of the Arachnida, since it has been already invalidated 

 by the co-existence of pulmonary sacs and tracheae in the genera 

 Segestria and Dysdera ; whether, in a word, until more is made 

 out of the anatomy of Obisium to establish its further affinity to 

 the Scorpionidce, its present position among the Trachearia may 

 not be regarded as a provisional one ? As yet, I am strongly 

 disposed to believe that subsequent facts will prove that the pre- 

 sent and allied forms are the true dwindled acaudal representa- 

 tives in this country of the gigantic and formidable species which 

 infest the tropics. 



1 Arthur Street, Gi'ay's Inn Road. 



IX. — Observations on Fucus Labillardierii, Turner. By the Rev. 

 M. J. Berkeley. In a Letter- to R. Taylor, Esq. 

 My dear Sir, 

 The following extracts from a letter with which I have been fa- 

 voured by Dr. Montague relate to a subject of much interest as 

 regards the physiology of Algse, and are in themselves so excel- 

 lent that they cannot fail to be acceptable to many of your read- 

 ers. The plant to which they principally refer is Fucus Labil- 

 lardierii, Turn., which was improperly referred by J. Agardh to 

 Suhria, and has lately been raised to the rank of a genus, under the 

 name of Ctenodus, by Kiitzing, on characters taken almost en- 

 tirely from the structure of the frond, without reference to any 

 peculiarities in the fructification. The genus Calocladia, Grev., 

 founded upon an Alga supposed to be identical with Turner^s 

 plant, though in reality very different, is, it appears, the same 

 with Delisea, Lamouroux. Mr. Harvey had ascertained the real 



