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THE POPULAR SCIENCE MONTHLY 



thousands of them and a great many different forms though it is 

 quite easy to find them almost everywhere, it is still very difficult 

 to make out their manner of existence. For example, how they 

 perform the feat of locomotion is not well understood. There are 

 two ways of explaining this : one is, that the diatom moves from 

 place to place, owing to the osmotic changes constantly taking 

 place inside the shell ; the other and perhaps better authenticated 

 opinion is connected with the peculiarity already referred to that 

 is, the presence of little apertures in the wall through which por- 

 tions of the protoplasmic contents protrude. Those who believe 



in the osmotic theory claim 



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Fig. 5. Stictodiscus Californicus. 



that no such apertures exist, 

 and consequently no proto- 

 plasm finds its way to the 

 outside of the shell. In 

 connection with this point 

 comes the story of the visit. 

 While working in the 

 Botanical Laboratory of 

 Berlin this past summer, 

 the writer was invited to 

 visit a gentleman having 

 the reputation of knowing 

 more about diatoms than 

 any other person now liv- 

 ing. It is rather a strange fact that this gentleman is not a 

 learned professor who has spent a long life over scientific prob- 

 lems, but a retired book-seller who owns a beautiful villa in the 

 suburbs of Berlin, and has for many years been gathering in- 

 formation of various kinds about this wonderful little plant. He 

 has nearly all the literature treating this subject, several large 

 volumes of which are now out of print, and for which he told me 

 he had been obliged to pay exorbitant prices. 



Before proceeding to the inspection of the laboratories, speci- 

 mens, models, etc., coffee and cakes were served in the garden, a 

 distinctively German hospitality which no scientific interests are 

 allowed to interfere with. We then began in the preparing labo- 

 ratory, a small but very completely fitted room, where the mate- 

 rial for investigation is stored, treated, and classified for use. 

 Here are the chemicals used in preparing the plant for examina- 

 tion. Some processes serve to preserve the form and general 

 structure of the living part within the shell, so that this may be 

 studied ; other reagents, on the contrary, destroy the living por- 

 tion, whereby the shell may be more easily examined. In this 

 laboratory was a microscope of somewhat older style than our re- 

 cent ones, but a very good, reliable instrument, which he told me 



