THE 336 DIATOM TYPE SLIDE BY J.D. MOLLER
AUTHOR: Barry Sobel
INTRODUCTION:
J.D. Moller (1844-1907) is known to have mounted type-slides of diatoms starting in 1867. These could contain only one species, several, hundreds or, rarely even thousands of diatoms. The slides were supplied with written lists of the species. Only a few versions of Moller slides with the names photographed onto the slide were made. These include a 5 diatom test slide, and 40 species, 100 species and a 335 species type slides. The slide with the most diatoms contained 4026 species and was sold to Professor Van Heurck. Moller himself also made micrometers. After his death in 1907, his son Hugo took over the business and supplied a range of technical optical equipment and slides into the 1960s. The March 1951 catalog was issued as a microphotograph. Hugo offered many different types of slides, but also continued to offer diatom slides including type-slides. Although Moller is said to have made thousands of type slides, few appear on the market, and they are highly collectible. Barry's slide collection includes the 336 specimens version featured on this web page, a sample slide of 23 diatoms, and a 5-form test slide in microphotograph mount.
Type slides were made by other makers into the 20th century, as well and the author has a 535 specimen slide made by Klaus Kemp in 2004. He also has a 100 type slide by Thum from the late 19th century.
The early Moller type slides were often labeled by diamond-engraving on the slides themselves as shown in the example shown to the left from the early 1870s. Later, the slides had labels affixed as in the present example. There were relatively few with photographic grids for the diatoms themselves but these included not only type slides but also test slides as in the example on this site. For more information on the Moller company please see
Brian Stevenson's review on Microscopist.net.
DESCRIPTION:
This slide contains 336 diatoms divided into four sections. All four sections all contain at least 80 diatoms, but first has an additional 10 to make 90, and the second an additional 5 to make 85. This totals 336. The diatoms are mounted on the bottom of the photographic grids. Each of the 4 grids also has Moller's signature under the right hand bottom edge, a sample of one shown to the left. Many of the specimens are shown both in valve view and girdle view. All the diatoms are present, but many have come off the photographic grid and are located deeper in the slide and, mainly on the bottom right grid, some of these have also moved away from the center of their respective grid square as well, with some in the right lower grid halfway into an adjacent grid square. When focusing on the grid, one notices that all the diatoms are slightly out of focus because they are on the bottom of the grid, all the printing being on the top of the photograph. One would surmise from all of this that, most likely, the grid was mounted on the coverslip, and then the diatoms mounted on the bottom of the coverslip which was then mounted on the slide. As anyone knows who has attempted to mount diatoms in a precise manner, this takes tremendous patience and skill!
Shown below are images of the 4 coverslips on the slide, the grids all shown together, individual grids and examples of some of the diatoms on the slide. DIC illumination at 40X shows the detail of most of the diatoms, though in some cases, oil immersion would be needed to resolve the puncta.
