ON A NEW INSTANCE OF SYMBIOSIS. 

 By William A. Haswell, M.A., B.Sc. 



Some time ago I had the pleasure of bringing under the notice 

 of this society an instance of Symbiosis, in which the organisms 

 were a minute Sea-Anemone and a Bryozoan. (1) The example 

 which I have now to bring forward is not without analogy 

 with this. Last year I described in a preliminary note (2) the 

 general appearance of a new and remarkable species of Phoronis, 

 the first that had been found to inhabit Australian Seas. I 

 described the worms as inhabiting spaces or channels in the 

 substance of a wide tube about six inches long, formed of felted 

 threads and having a smooth interior — the heads of the Gephyreans 

 projecting externally. The tube when first discovered was quite 

 empty, and I could not even conjecture what the meaning of this 

 singular structure could be. Fragments of similar colonies have 

 been dredged repeatedly since, and Mr. W. H. Caldwell, who while 

 at Naples made a special study of the Mediterranean Phoronis 

 hippocrepis, has more than once obtained large pieces containing 

 many individuals. It was only the other day however, that the 

 mystery regarding this remarkable mode of growth of the Phoronis 

 was solved. Mr. Ramsay obtained in a dredge a fortnight ago, 

 specimens which proved not only to contain colonies of Phoronis 

 australis, but also the inhabitant of the cavity of the tube in the 

 substance of which the Phoronis grows. This proves to be a large 

 St a- Anemone, of the genus Cerianlhus. 



We have thus here a very remarkable instance of mutual 

 co-operation in two animals belonging to widely different classes. 

 A Sea-Anemone lives in the lumen of a tube the substance of 

 which is inhabited by a colony of Phoronis. It is not an instance 

 of mere parasitism or commenalism ; we have plenty of instances 



(1.) Proc.Linn. Soc, N.S.W., Vol. VII., p. 608. 

 (2.) Op. cit., Vol. VII., p. 611. 



