Nudibranch eggs - direction of spiral

Dear Asther,
Have a look at the egg spiral page. You will find a number of relevant messages there and a number of links to other messages.

Most opisthobranch egg masses seem to spiral in an anticlockwise direction [sinistral] - that is coiling in a anticlockwise direction from the centre. However some such as Melibe australis and Melibe engeli seem to be dextral, coiling clockwise from the centre.

However you will see there is some discussion about whether in the northern hemisphere they spiral anticlockwise and in the southern hemisphere clockwise, but there is not a lot of evidence to support that idea. Another complication is whether the egg ribbon is started at the outside or in the centre. Usually the egg ribbon is started at the centre, but in a few animals the egg ribbon is started at the outside. If a ribbon is started at the outside then it will look the reverse to what it actually is. Nothing is simple I'm afraid.
Best wishes,
Bill Rudman