Behavior ID of nudibranch (Pteraeolidia ianthina)

I am a newbie on this forum...kick me out if this is not the thread for this sort of questions...seemed most appropriate to me...

The two pictures of the nudibranch (Pteraeolidia ianthina) were taken within a minute. Can someone tell me what it is doing on the right hand picture? What is this white bit at the tip of the arrow? An idea I heard so far: inverting the stomach like other species?

My guess it is the everted oral tube as described here: http://www.seaslugforum.net/showall.cfm?base=pteriant.

I recommend you contact Bill Rudman at the Sea Slug Forum for more information.

Thanks for the hint, I have posted on the seaslug forum. Bill Rudman has given his valuable opinion on this matter. It looks like the white bit I was wondering about belongs to the anterior foot of the nudibranch.