1897J MlCHOSCOPlCAL JOtJRNAL. 3? 



pulsion of air from the frustule, and a substitution of 

 the balsam in the air spaces. If these phases of study 

 are accurately construed, we have a demonstration of 

 the presence of enveloping substance on the exterior of 

 the silicious frustules without resorting to staining tests 

 for a like purpose. 



Continuing this investigation, I made an attempt to 

 differentiate the protoplasmic mantle with the aid of 

 dyes in order to verify an experimental study recorded 

 several years ago by C. Onderdonk and published in this 

 journal. While I failed to duplicate what was stated 

 therein, I found a wide range of interesting phenomena 

 throwing light on the structure of the living diatoms. 

 By placing a drop of water with numerous large Navic- 

 ulsB on a slip and covering it with a I inch cover glass, 

 and then placing in contact with the edge of the cover- 

 glass, a minute grain of crystalline methyl-blue, the dye 

 was speedily diffused from the edge of the glass and 

 passed slowly across the fluid field. Then it was a very 

 easy matter to steadily observe for protracted intervals 

 the action of the dye, as its influence reached the living 

 frustules. For example, the stain was absorbed by the 

 frustule both inside as well as outside, some time before 

 it was perceptible in the thin layer of liquid; and more 

 markedly absorbed by the internal protoplasmic granules 

 when the dyeing action became more evident. The evi- 

 dence of a strong irritation on the part of the frustule is 

 readily observed as it quickly loses the power of direct 

 axial motion and swerves irregularly and spasmodically 

 at alternate ends^ unable to advance in its normal man- 

 ner. It may even spin around in its own length, the 

 power of controlling its normal traveling motion being 

 in a manner paralyzed. At least this would be the pro- 

 bable interpretation, that any observer would identify 

 with an irritating toxic substance acting on organisms 

 having a determined or even conjectural nervous system 



