I think this was done with animated metaball. You can find them in the Add menu , meta object …
My guess is metaballs were dupliverts of a particle emitter inside a larger metaball. Some of the metas are set to negative as well.
that worked CD38
that file was the subject of a post not to long ago answering a question I had. try
https://blenderartists.org/forum/viewtopic.php?t=59118&highlight=meta