This is a close-up of a red seaweed called Polysiphonia opaca. Seaweed are algae and Polysiphonia is a large genus which contains many poorly defined species.

 Apparently, Polysiphonia have one of the most complex life cycles of any living organism, so the author won't be brave enough to state which of the reproductive structures is shown in the image!

 The photograph was taken using dark-field illumination which is very effective for transparent specimens. Micscape may have an article shortly on this type of illumination for novices.

 Image details
Photograph taken by D W Walker. 64 colour version of 24 bit master on PhotoCD. Slide prepared by Brian Darnton and circulated by the Postal Microscopical Society.

Comments to the author Dave Walker welcomed.