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III. On the Structure and Systematic Position o/Stephanoscyphus mirabilis, the Type 

 of a new Order o/Hydrozoa. By Prof. Allman, M.D., LL.D., F.E.S., 8fc, Pres. 

 Linn. Soc. 



(Plate XIV.) 



Eead November 19th, 1874. 



VvHILST engaged last May in zoological researches on the coast of Antibes, I was 

 struck by some small patches of one of the horny sponges which had attached them- 

 selves to stones at a slight distance below the surface of the sea, and which had arrested 

 my attention by what appeared to be unusually distinct and well-defined oscula. After 

 transferring some specimens to a phial of sea-water, I was astonished to find that from 

 each of the apparent oscula a beautiful crown of delicate tentacles soon began to develop 

 itself. The tentacles were quite like those of certain hydroids ; and the appearance was 

 such as might easily have led to the belief that the anticipated form had at last been 

 found which would decide the zoological position of the sponges, and remove all doubt of 

 the hydrozoal structure recently assigned to them *. A closer examination, however, 

 showed that the orifices on the surface were not really oscula, and that the tentacles 

 proceeded, not from the sponge itself, but from a totally different organism, which lay 

 imbedded in its substance, and which sent tubular prolongations to the surface, where 

 they opened in the manner of genuine oscula. 



It was further evident that the organism thus associated with the sponge was in the 

 highest degree interesting ; and a careful study of its structure made it plain that, while 

 in all essential points it possessed a true hydrozoal organization, it differed from all the 

 recognized orders of Hydrozoa so widely as to necessitate our assuming it as the type of 

 an entirely new one. 



To this remarkable animal I have given the generic name of Stephanoscyphus. When 

 freed from the surrounding sponge, it is seen to be composed of an assemblage of zooids, 

 which are included in chitinous tubes, and associated into a composite colony by a common 

 basal plexus of tubes, the aspect of the whole being very much that of an ordinary hydroid 

 trophosome (figs. 2, 3). In all the specimens examined the common plexus lay at the 

 base of the sponge, and the tubes given off from this penetrated the sponge-tissue, and, 

 rapidly increasing in width, ultimately reached the surface, on which they opened. The 

 tubes really extended beyond the general surface ; but each carried up the sponge-sub- 

 stance with it, so that the orifices appeared elevated on the summit of conical papillae — 

 a condition very common in the oscula of sponges (fig. 1). 



The distal extremity of the animal can extend itself beyond the orifice of the chitinous 

 tubes, and can again withdraw itself far into the interior. When extended (fig. 3, a), it 

 displays a coronal of tentacles, which surround a wide terminal orifice. The tentacles 

 spring from the very margin of this orifice ; for there is nothing like a hypostome or pro- 



* Haeckel, ' Kalkschvramme.' 



