A look at an old slide

by Mike Samworth

A friend quite recently gave me some dusty prepared slides. Most of these were quite uninteresting slides, either fairly standard histological material for school use or were slides that had not lasted too well, despite only being twenty or thirty years old. However, there was one that immediately took my eye, and I put it to one side for looking at later. As often happens, the "later" is often VERY much later!

The slide has just one label on it, a rather fancy affair with the following hand-written on it; Polycistina from Barbados.

The following scan shows the label;

Slide label.

A slide of polycistina from the rocks of Barbados was a very popular object with Victorian microscopists, being considered one of the most beautiful objects for study. According to the author of one Victorian book, people have been tempted to purchase microscopes from having seen for the first time, a collection of these matchless structures. They are actually fossils, being the homes or skeletons of Radiolaria.

During the 'Challenger' expedition vast numbers of Radiolaria were found in the ocean surface dredgings. Within a framework of only a hundreth of an inch in diameter there may be dozens of spines radiating from the centre, often beautifully sculptured and branched. Others appear as spiny balls made up of an elaborate latticework of glassy texture. The photomicrograph below shows how much like Chinese ivory carvings some of these look like.

Polycistina from Barbados.

Radiolaria are all marine; most of them live near the surface in tropical seas, and their skeletons sink to the bottom in what is sometimes referred to as a raining down of material. They can form extensive deposits and their study is of great importance to the oil industry in particular.

This old slide is a nice one that I enjoy looking at. I do not have any idea whatsoever who made it, or indeed how long ago, but it is in quite good condition, and testament to the skills of slidemakers.

Photomicrograph by Mike Samworth.

If any reader wishes to ask about any of the above, or to comment, please do get in touch by contacting me Mike Samworth

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