16 Theodor Fuchs, 



Phorouis psammophila Cori. Hyaline Röhre mit Sandkörnchen umgeben, rasenbildend. 

 Phoronis australis Haswell. Wohnen gesellig in Cerianthus-Röhren. 



Diese letztere Art ist es nun, die uns hier vorzugsweise interessirt, und ich glaube das Vorkommen 

 dieser Art nicht besser schildern zu können, als indem ich die Beschreibung, welche Haswell von diesem 

 merkwürdigen Vorkommen gibt, hier wörtlich wiederhole: ' 



»Last year I described in a preliminary note the general appearance of a new and remarkable species 

 of Phoronis, the first that had been found to inhabit Australian Seas. 1 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 J could not even conjecture what the meaning of this singular structure 

 could be. Fragments of similar colonies have been dredged repeatedly since, and Mr. U. H. Caldwell, 

 who while at Naples made a special study of the Mediterranean Phoronis hippocrcpia, 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 contains 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 Sea-Anemone of the genus Ccrianthus. 



We have thus here a very remarkable instance of mutual co-operations 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 colon}' of Phoronis. 1t is not a instance of mere parasitism or commensalism; we have plenty of 

 instances in which one animal finds it adventageous to take up its abode in the walls of the dwelling of 

 another. But here we have something more. The tube in which the Anemone dwells is not formed by the 

 Anemone alone, but is partly manufactured by the Phoronis. This is proved by an examination of the 

 texture of the tube, which is partly made up of gelatinous threads containing a large amount of the 

 same dark purple pigment found in the integument of the tentakle and front part of the body of the Pho- 

 ronis, and partly of much finer threads. 



Among the meshes of the latter, which form the greater part of the thickness of the tube are nume- 

 rous oval thread-cells, and the thick feltlike substance seems to consist of nothing eise than the dischar- 

 ged flagella of these bodies. The Phoronis inhabit transparent membranaceous tubes which seem obli- 

 quely in the substance of the tube of the Cerianthus, projecting usually a little distance beyond the 

 general outer surface of the latter — the mouth directed more or less upwards. The openings of these 

 smaler tubes lie over the whole surface of the large tube ; except a short space at the lower end, the tubes 

 themselves form a substantial part of the thickness of the latter, and there can be little doubt from the 

 way in which the threads which seem to be derived from the Phorouis are interwoven with those produced 

 by the threadcells of the Cerianthus, and from the intimate manner in which the smaler tubes are inter- 

 woven with the tissnes of the larger one that the two slructures — the colony of Phoronis and the projecting 

 case of the Sea-Anemone — have grown simultaneously.« 



Man sieht, es sind in diesem merkwürdigen Fall von Symbiose alle wesentlichen Elemente enthalten, 

 welche zur Erklärung der von Kalkfäden umsponnenen Cylindriten erforderlich sind. 



Stellt man sich eine im Schlamme gegrabene Wohnröhre mit einer weichen Haut ausgekleidet vor, 



stellt man sich ferner vor, dass sich in dieser Haut Colonien von Phoronis ansiedeln, 



und stellt man sich ferner vor, dass auf dem Wege der gewöhnlichen Steinkernbildung sich einAbguss 

 dieses ganzen Kanalsystems bilde, so muss das Resultat hievon notwendiger Weise ein wurmähnlicher 

 Kalkcylinder sein, der von feinen Kalkfäden umsponnen ist, d. h. es muss ein genau solches Object ent- 

 stehen, wie zuvor beschrieben wurde. 



] W. H. Haswell , On a new Instance of Symbiusis. (Proceed. Linn. Soe. New-South-Wales. IX, 1885, 1019.) 



