ON A LARVAL ACTINIAN PARASITIC IN A RHIZOSTOME. 223 
recalls the discovery in a similar situation of another and 
possibly closely related Actinian found by the Astrolabe 
Expedition ( 4 ) off the east coast of Australia in 1833, and 
recently investigated by Pax (5). The escaping larvae varied 
in length from 20 mm, to 40 mm. 
Description of Larvae. 
Both the adult and the larval form of P. hilli found free- 
living have been described by Miss L. J. Wilsmore from 
specimens obtained from Broken Bay by Prof. J. P. Hill. 
In regard to the colour of the larva, the body is light 
amber, the oesophageal folds somewhat flesh-coloured or 
tawny, and the twelve tentacles have purplish-brown mark- 
ings. There is a spot at the apex of each tentacle, and next 
to this is a line encircling the tentacle. The five markings 
which follow are V-shaped, and are on the oesophageal surface 
of the tentacle only. The colour of the apex of the V is weak 
or absent. There are no processes on the body resembling 
the suckers described by Haddon and Dixon (6) in the adult 
P. hastata; and neither while the larva is in its host nor 
“in vitro,” have I seen any attempt on the part of the larva 
to attach itself except by its oesophageal folds. 
There are two points which call for a further description, 
and which are, moreover, of considerable interest in con- 
nection with the parasitic life of the larva : I refer to the 
conchula and the pores present in the physa. Both of these 
structures are best studied in the living animal. 
The Conchula and Pores of the Physa. 
In the genus Peachia there is a single deep siphonoglyph. 
When the lips of the siphonoglyph come together, there is 
formed a tube which runs from the enteron to the exterior. 
In some species the external opening is surrounded by a 
complicated series of lobes, forming a conchula. In others 
the conchula is of a simpler nature. 
