ON A LARVAL ACT1NIAN PARASITIC IN A RHIZOSTOME. 221 
On a Larval Actinian Parasitic in a Rliizo- 
stome. 
By 
C. Badlmm, 15. Sc., 
Demonstrator in Zoology, University of Sydney. 
With 3 Text-figures. 
Our knowledge of the medusophilous larval Actinians lias 
been summarised by Haddon ( 1 ) and by McMurrich ( 2 ). 
The last-named author says : “ The available evidence seems 
accordingly to point strongly in favour of the various medu- 
sophilous forms being the young stages in the development 
of Peachia rather than Halcampa; but a direct linking-up 
of the immature examples of Bicidium 1 with their respective 
adults is necessary to settle the question.” 
In this paper I will show that I have found the larvae of 
Peachia hilli parasitic in a Rhizostome up to the stage in 
which they have been found free-living — thus linking up this 
medusophilous form with the adult. There is described, for 
the first time, the function of certain structures (the conchula 
and pores of the physa) found in Peachia larvae, and 
their importance in connection with the parasitism of the 
widespread genus Peachia is emphasised. So far as I am 
aware, this is the first time that a larval Actinian has been 
•described as parasitic in a Rhizostome. The parasitic larvae 
hitherto described differ from the larvae of P. hilli in this 
1 A genus in which he places these medusophilous forms. 
