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On the Stomodceum of the Alcyonarians. [June 14, 



III. " On the Ciliated Groove (Siphonoglyphe) in the Stomo- 

 dseum of the Alcyonarians." By Sydney J. Hickson, B.A., 

 B.Sc. Assistant to the Linacre Professor, Oxford. Com- 

 municated by Professor Moseley, F.R.S. Received May 23, 

 1883. 



(Abstract.) 



1. In Alcyonium there is a groove lined by remarkably long cilia, 

 situated on the ventral side of the stomodaeum. This groove, which 

 has already been superficially referred to by O. and R. Hertwig, has 

 important morphological relations in the group Alcyonaria which have 

 not been previously referred to. I propose to call it the sipho- 

 noglyphe. 



2. The cilia of the siphonoglyphe, as seen in a living Alcyonium, 

 moving in unison, produce a current from without inwards which 

 brings particles of food and fresh streams of water into the canal 

 system of the colony. The cilia lining the rest of the stomodaeum 

 produce currents in an opposite direction, from within outwards. 



3. A siphonoglyphe, varying in size and in the length of the cilia, 

 is present in the same position in all the non-dimorphic Alcyona- 

 rians (without solid calcareous or horny axes) I have examined, e.g., 

 Ccelogorgia, Briareus, Nephthya, Spongodes, Tubipora, Clavularia, 

 Heliopora, &c. 



4. Amongst the dimorphic Alcyonarians the siphonoglyphe is 

 usually absent in the autozooids, but well developed in the siphono- 

 zooids. In Sarcophyton, however, a feebly-developed siphonoglyphe 

 is present in the autozooids in addition to the well- developed ones* 

 in the siphonozooids. 



5. In Primnoa and Yillogorgia, the only examples of Alcyona- 

 rians with solid axes I have examined, no siphonoglyphe can be 

 found, and I am inclined to think, from the researches of other 

 observers, and from general considerations, that it is not present in 

 any genera in which the fleshy parts of the colony are represented 

 only by a thin crust covering solid axes. 



6. The paper contains some speculations to which I have been led, 

 by these researches, concerning the probable phylogeny of the group, 

 and a diagrammatic arrangement of the Alcyonaria on these lines. 



7. Finally I propose to divide the Alcyonaria into five principal 

 groups : 1st. The Proto-Alcyonaria, including only those genera 

 which do not form colonies. 2nd. The Stolonifera, including the 

 genera Clavularia, Cornularia, Tubipora, &c, in which the young 

 colonies spring from a creeping stolon. 3rd. The Pennatulidse, which 

 remains as heretofore. 4th. The Gorgonidae, a group which contains 

 only those genera in which there are solid horny or calcareous axes, 



