On the IStructure and Affinities of Mueatra parasites Krohn etc. ;i7 



Material. 



During- the spring of 1900 the prevailing- westerly winds uo 

 doubt contribiited to an imusually large number of Phyllirhoe buce- 

 phcäa and Physalia being eaptured in the Bay of Naples. Out of 

 thirty-one individuai« of PhylUrhoe taken between March 28 and 

 April 20, nineteen, or more than half, had a Mnestra adhering 

 to them. 



My friend Dr. Lo Bianco in the kindest way placed his störe 

 of S])irit-preserved material from the Bay of Naples at my disposai 

 for examination. The dates of capture were unfortunately not re- 

 corded but of forty-three full grown Phyllirhoe every one had or 

 had had a Mnestra upon it. 



A few microscope preparations made by the late Prof. Kleinen- 

 berg of Messina, which were also submitted to me for examination, 

 indicated in a not less convincing way that during certain seasons 

 in the Mediterranean, it is exceptional to catch a Phyllirhoe bucephala 

 which has not got a Mnestra actually adhering to it, or wliich does 

 not show some sign or scar at the spot where the Mnestra is usually 

 attached. 



So far as I am aware none of the several species of Phyllirhoe 

 eaptured in seas other than the Mediterranean have been recorded 

 as having been infested with the medusa. At present therefore we 

 are justified in consideriug Mnestra parasites as peculiar to the 

 Mediterranean. 



Descriptive and Comparative Aiiatoniy. 



The Mnestra is attached to the Phyllirhoe by its manubrium 

 which is relatively short. The blood of the host and apparcntly 

 other cells also, constitute the nutriment of the medusa and are 

 sucked through the Channels in the manubrium into the gastral 

 Spaces. 



The Umbrella. 



The shape of the umbrella is more flattened than is usuai 

 among the free swimming Cladonemidae , but it is rarely as 



