720 DR. w. c. m'intosh on a 



On a Eeraarkably Branclied Syllis, dredged by H.M.S. 

 ' Challenger.' By W. C. M'Intosh, LL.D., F.E.S., F.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 Catenida, with the propagation by division in Nais pro- 

 hoscidea and Ghcetog aster, as well as the more complex condition in 

 Autolytus, Myrianida, and Flligrana, 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 Eaplectellce and other 

 remarkable sponges of the kind. Besides the Syllis the sponge 

 was tenanted (as in JEuplectelld) by a small member of the Poly- 

 noidse, which will be described in due time. 



The Syllidian (Syllis rcimosa) 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 difficult 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 Syllis-Wkc annelid of tlie thickness of 

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

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



