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NOTES AND MEMOEANDA.* 
Diatoms in Coloured Liquids. — Dr. Hamilton L. Smith (U.S.) 
writes to the Belgian Microscopical Society : — “ The communication 
which exists between the internal protoplasmic substance and the 
exterior does not take place along the sutures of the connectives, hut 
in Navicula (properly so called) it exists along the raphe or median 
line of the valves, and in Surirella and Nitzschia along the edges of 
the wings or of the carinae. 
“ I possess some drawings showing the injection of indigo along 
the median line and its penetration into the interior of the diatom, 
especially in Stauroneis which had lain some days in water saturated 
with indigo. Apart from this demonstration, I have been able to 
obtain, by employing this pigment, an idea of the mode of progres- 
sion of some large s])ecies of Pinnularia. 
“ On observing a living Pinnularia under the microscope, when 
the field has been made blue with indigo, and the object is looked at 
on the valvate side (that is to say, with the median line turned towards 
the eye), small particles of indigo are seen to run all along this median 
line and to accumulate near the centre in the form of a small ball or 
sphere. Looked at from the side of the connective (front view), a 
ball is seen to form in the centre of each valve ; and what is remark- 
aide, each of these small spheres turns on its axis with a tourhillon 
motion, just as would be the case if a small jet of water issued beneath 
it from a small orifice situated at the central point of the median line. 
“ When the balls have attained a certain volume they suddenly 
burst, and the particles of indigo then proceed with a retrograde 
motion along the frustule. Immediately after the rupture of the ball, 
a new one begins to form in the same place. The particles take a 
given direction, whilst the diatom itself follows the contrary direction. 
If the motion of the diatom is reversed, the particles of indigo follow 
an opposite course to that indicated. I have observed this curious 
phenomenon for hours together, and it was a glorious spectacle. I 
had in the field of the microscope some magnificent specimens of large 
Pinnularia, and the phenomenon showed itself specially distinct, when 
in consequence of a grain of sand or other obstacle the free motion of 
the frustule was arrested. The colour I used was the ordinary blue 
indigo water-colour paint, applied in a pretty concentrated form. 
“ Another observation which I made at that time proved to me the 
existence of a gelatinous external hyaline envelope to the frustule, which 
prevented the direct contact of the particles of indigo with the siliceous 
* It is intended that each number of the Journal shall in future contain 
notes of the articles in foreign journals which relate to tlie microscope or the 
various subjects of microscopical research. Also notes of new books or new 
editions and of the contents of the English and foreign microscopical and other 
journals which can be referred to in the Society’s library. The Journal will thus 
contain a record of the progress of microscopy both in England and abroad, and 
the Fellows will be able to ascertain from time to time what has been published 
of interest to them in the various periodicals. 
