A Rare Sponge from the " Scotia " Collection. 231 



XVIII. Note on a Rare Sponge from, the " Scotia " Collection. 

 By Professor J. Arthur Thomson, M.A., and Mr J. D. 

 FlDDES, M.A. 



(Read 18th December 1905.) 



In the collection of Alcyonarians made by Mr W. S. Bruce 

 on the " Scotia " Expedition, there was an interesting and 

 rare sponge, which is deserving of record. It was dredged 

 from deep water between Gough Island and Cape Town. 

 The specimen consists of two separate parts of a straight 

 upright axis, giving off numerous irregular branches, most of 

 which are short. The axis is 26 centimetres in length, rigid 

 in its thicker lower part, becoming slightly flexible as it 

 tapers upwards. One of the branches is long, and bifurcates 

 at a distance of 7 cms. from the stem, being continued in 

 two slender divisions (one with a secondary twig) for about 

 4 cms. 



The siliceous spicules composing the stem show at once 

 that it is the core of a Monaxonial sponge, from which, 

 unfortunately, almost every trace of the soft tissue has been 

 weathered or rubbed off. On two or three areas there was a 

 thin coating of soft, white, friable material, which revealed 

 nothing. The texture of the stem is tough and stringy ; the 

 surface is rough, with minute monticular eminences, which 

 give it a somewhat file-like appearance. 



Closer examination shows that the axis is composed of 

 densely-packed style-like spicules, imbedded in a spongin 

 framework, and a transverse section shows that the spicules 

 have an annular arrangement like the lines of growth in a 

 tree-trunk. The branches are formed by bundles of spicules, 

 which diverge from those of the main stem. 



The majority of the spicules are needle-like, with a 

 rounded and a pointed end, growth evidently occurring 

 towards the point. In more technical language, they are 

 monactine monaxons, growth proceeding along the axis in 

 one direction only, and they are rounded or strongylote at 

 one end. In a word, they are " styles." They have a great 

 tendency to split along the axis when boiled in caustic 



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