I think they look like tiny bubbles at first, but I'll give you a hint and reveal that those clear, shiny, reflective parts are actually transparent shells.
The grayish, opaque parts are the animals' body parts:
In some views (as below), you can see two small, rounded lobes — they can look a bit like a little "bowtie." These are the velar lobes (or velum) that the animal uses to swim.
In each view, I've zoomed out a little further. Now I'm showing the entire egg mass:
These are the larvae, or veligers, of Fiona pinnata, the pelagic nudibranch I wrote about on 22 September. I photographed a few of the older egg masses to document the later stage embryos, but I haven't had a chance to show you these pictures yet. I was impressed with the height of their shells! The veligers hatch from the egg mass, swim in the plankton for a while, then undergo metamorphosis into a juvenile nudibranch similar to the one I showed in last month's post (they'll lose these beautiful larval shells at metamorphosis).