112 Proceedings of the Royal Society of Victoria. 



(4) Note on some Actinian Larvce parasitic upon a 

 Medusa from Port PJiillip. 



By Arthur Dendy, M. Sc. 



Demonstrator and Assistant Lecturer in Biology in the University of 

 Melbourne. 



[Read November 15, 1888.] 



It has been known for a long time that the larval forms of 

 certain species of Actinians are habitually parasitic upon 

 Medusjie, thereby obtuining the advantages of free swimming 

 without being obliged to possess locomotive organs of their 

 own. I need enter into no details as to the observations of 

 previous writers on this subject, as Professor Haddon* has 

 already published a most valuable bibliography of larval 

 Actinia;* parasitic on Medusse. 



According to this author, such ])arasitic larva? have hitherto 

 been found in North European seas, in the Mediterranean, 

 on the coast of New England, and in the Southern Ocean. 

 The object of the present brief note is to place on record the 

 discovery of three parasitic Actinian larva^ on a Scyphomedusa 

 from Port Phillip, wdiich I had the good fortune to tind on 

 tlie occasion of the University Science Club's excursion to 

 Cheltenham. 



The Medusa upon which the specimens were found is a 

 small monostomatous form about two inches in diameter. 

 The bell is flattened, and the rnaroin is notched into eio^ht 

 lobes, each subdivided into two halves by a dee]) indentation 

 containing a tentaculocyst. The mouth is squarish, and at 

 each corner is a rather large, somewhat flattened projection, 

 with a much folded or crenated margin. These four projec- 

 tions are, of course, the oral arms. From the under surface 

 of the Medusa, about half way between the oral arms and 

 the margin, there ai'ises a circle of ver}^ numerous, long, 

 slender tentacles, arranged in eight horseshoe-shaped groups 

 placed adradiall3^ Each group contains about twenty-flve 

 tentacles, and the concavity of the horseshoe faces outwards. 

 In the living animal the bell has a yellowish-brown tinge ; 

 the oral arms are of a warm sepia colour, sometimes with a 



* Scientific Proceedings of the Royal Dublin Society, N. S., vol. 5, p. 473. 



