Nudibranchs are hermaphrodites. They have both male and female sex organs.
Nudis use chemoreceptors in their rhinophores to find a mate.
Since the sex organ is only on the right hand side, they line up next to each other head to tail, tail to head. They can only copulate in the '69' position. <insert juvenile laughter here>
After they fertilize each others' eggs, they crawl away, smoke a cigarette, and lay elaborate egg masses that look like a rose. If you ever happen upon one nudibranch laying eggs, there is often another one nearby doing the same thing.
Note that after mating, fertizilation may not take place immediately. The sperm from another nudibranch of the same species may be stored in a special organ called the seminal receptacle for months until the environmental conditions are just right.
Nudibranchs in the Aeolid suborder have elaborate courtship foreplay before mating. They participate in gentle touching of each other's bodies with questing cephalic tentacles. These whole body caresses are all part of getting to know each other. Copulation can take minutes, hours, or even days!
Today is the day! I am about to leave for O'Hare. I tried to check in online and I realized that my trip from here to Bali is a 35 hour trip (and that's if everything goes well)!
I loaded up my new iPad with lots of books and Angry Birds, so I should have plenty to keep me busy.