172 
SYDNEY .T. HICKSON AND .T. T. ^YADS^YORT^. 
ex:cept that we have observed a slight disc-like swelling at the 
point of attachnient. 
After full consideration of all these points of apparent 
differences, and bearing in mind the possibility of considerable 
variation in adaptation to the conditions, we have come to the 
conclusion that the Urnnla found on Dendrosoma should be 
referred to the species U. epistylidis (ClaparedeandLach- 
mann). 
It is not necessary to give a full description of the species, 
but we will be content with a few remarks on some special 
character’s. The tentacles are the most remai-kable featnr’es. 
In the first place they are compai-atively rai’ely seen, the body 
of the Urnnla being usually rounded off within the test and 
at rest. In the majority of specimens which do exhibit 
tentacles at all only one is seen. When there ar*e two they 
usually cross one another as shown in fig. .39. 
It is extremely probable that a specimen that at one tinre 
exhibits only one tentacle may at another time exhibit two, or 
even three, tentacles. The tentacles of Urnnla differ from 
those of the typical Acineta.ria in two respects. They are 
relatively ver*y long and flexible, moving actively with cnrions 
sei’pentine curves as if in search of food. They do not 
terminate in a sucker. 
When fully extended they are very delicate and attenuate 
at the distal extremity to a very fine point (fig. 35). When 
partially retracted or not fully extended they are much thicker, 
show a spiral marking (fig. 45), and terminate in a spindle- 
shaped, or sometimes bluntly club-shaped, extremity. There 
can be no doubt that thev are protruded and withdrawn into 
the body with considerable rapidity. 
We have not been able to satisfy ourselves as to the food 
of Urnnla. We have frequently observed a tentacle bent 
over towards the head of the Dendrosoma, with its pointed 
end buried among the bases of the Dendrosoma suckers. 
This attitude suggested that the Urnnla is parasitic on the 
Dendrosoma, and this suggestion is confirmed by the fact 
that the heads of Dendrosoma affected by U rnnla do not look 
