Initialy I did some tests with Meta Balls with various colors and also some Spheres and the results were very dissapointing even bringing the image into photoshop to brighten didnt look good.  Especialy the spheres... I found no matter what color I picked I would get orange rings inside the sphere.. something I havent figured out yet.  I tried editing the sky preset so that I didnt have to bring it into photoshop for post work and that didnt  yield  good results either.

Skipping forward after a bunch of tests and such here is how I did the final image you see.

1. Using Bryce v6.1 I used a couple of objects included with Bryce.

2. Under  Objects > Misc >  I used  "Sweeping Spiral" and than I placed "Twisted Spiral" inside that.

3. Since I was going to use the Photoshop Invert method.. I used the inverted color chart posted in this thread as a guide line.

4.  I used the Default X-Ray preset to create the final colors I was aiming for.

5.  The instructions confused me about using Camera Controls vs moving the object placement.  Regardless I used the Dolly Tools to move the view to where I wanted and paid close attention to the NANO Preview window as the position of my Object did make a big
difference in the end result.  I did a few large renders till I was happy with what I got.

6.  As per text file, I increased the Ray Per Pixel to maximum which is 256, and rendered to a file.

7. Once in Photoshop... I inverted the picture first.  Now I could have rendered a "Object Mask" by this time I was tired and went the quick method.   I used the "Color Range" Method in photoshop to select the Black Background, and than I inverted my selection so that only my object bits were selected.

8. I played with the Brightness/Contrast tool to get the desired result.

Fran: That is the idea... if you have JellyFish Models try them out... I bet it would look great.