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any glasses in use on the Continent. But with them, particularly the 
latter, delicate membranes seen edgeways exhibit a blue tint, under 
certain circumstances, often giving rise to a difficulty in arriving at a 
decided opinion in questions connected with cellulose, when using 
the sulphuric acid and iodine test. Many phenomena might be 
cited in reference to this subject, but the main point to which he 
wishes to direct attention is, the doubt existing in his mind as to the 
nature of the red spot described by Ehrenberg as an “eye” in the 
Infusoria. He has observed this object chiefly in the unicellular Alge 
and zoospores, and was first led to suspect that the red colour 
depended on unequal refraction, in the cells of Chlamydomonas Pul- 
visculus. In these he has frequently found several red spots on one 
individual cell, which however could not all be brought into focus at 
once, and he has decidedly observed, that when these spots were 
brought into clear and well-defined focus, they appeared as bright co- 
lourless granules. Frequently no red spot at all could be found. 
The idea suggested by this was further confirmed by noticing the 
similar variations of colour according to form in a granule (nucleolus ?), 
in a half-decomposed, colourless, diseased cell. 
Finally, he had recently found that he could bring out the crimson 
colour most beautifully in the central spot or “hilum” of starch gra- 
nules. When the lens is a little too far away from the object, 
the hilum appears like a minute black spot; then, carrying the lens a 
little nearer, it comes out as a beautiful crimson spot exactly like an 
“eye-spot” in every respect. Adjusting the focus exactly, by bring- 
ing down the lens a little more, the hilum is seen as a well-defined 
spot of a brighter character than the rest of the starch-grain, but 
altogether devoid of any prismatic colour. 
Although dwelling but briefly on this question here, Mr. Henfrey 
states that he has had it under consideration for some time, and he 
thinks it desirable to make known his supposition now, in order that 
other microscopists working with different lenses may direct their at- 
tention to the point, and furnish the results obtained with them, since 
almost all high objectives differ slightly in their correction. 
On the Crescentiacee. 
Read further, “ Notes on the Natural Order Crescentiacee.” By 
Berthold Seemann, Esq., Ph.D., F.L.S., &c. 
