720 



DR. W. C. M'iNTOSH on A 



On a Eetnarkably Branched St/Uis, dredged by H.M.S. 

 ' Challenger.' By W. C. M'Intosh, LL.D., E.E.S., P.L.S. 



[Published by permission of the Lords Commissioners of the Treasury.] 

 [Read June 19, 1879.] 



When, in the summer of 1878, Sir Wyville Thomson wrote me, 

 inquiring if I knew of any branched annelid, I believe that the 

 substance of the knowledge then extant was expressed when I 

 mentioned that, though familiar with budding in such Turbel- 

 larians as Catenula, with the propagation by division in Nais pro- 

 hoscidea and Chatogaster, as well as the more complex condition in 

 Autolytus, Myrianida, and Filigrana, I could not say that I had 

 seen or read of a well-marked case of the kind. The subsequent 

 arrival of a Hexactinellid sponge containing the annelids, and 

 the various slides with mounted specimens, placed all doubts at 

 rest ; and, at Prof. Sir Wyville Thomson's request, I now make 

 a note on this remarkable form. Unfortunately, the annelid was 

 not observed till the return of the Expedition, and after immer- 

 sion in spirit. 



The Hexactinellid sponge was dredged at Station 209, in 95 

 fathoms, near Zebu, one of the Philippines, on greyish muddy 

 ground, celebrated for the abundance of Faplectellce and other 

 remarkable sponges of the kind. Besides the Sgllis the sponge 

 was tenanted (as in Euplectelld) by a small member of the Polj^- 

 noidse, which will be described in due time. 



The Syllidian (Sgllis ramosa) is located for the most part in 

 the basal canals of the sponge, above the " wisp." In this region 

 masses of the annelid, about a quarter of an inch in diameter, 

 occur, and a multitude of branches pass into the smaller canals 

 adjoining. Two of such masses are especially conspicuous. The 

 intricate manner in which the branches are arranged makes it a 

 very difiicult matter to dissect them out, especially when the 

 friability of the annelid and the sharp spicules of the sponge are 

 taken into account. Even after removal from the sponge it 

 is a laborious operation to unravel them without frequent 

 rupture. 



The masses and their numerous branches, as well as the iso- 

 lated portions, consist of a Sgllis-Wko; annelid of the thickness of 

 common sewing-thread. No head can be observed either in the 

 parent-stock, amongst the masses, or in the canals elsewhere, so 



