3 48 THE AMERICAN MONTHLY [Oct. 



something that is easily applied, as alcohol; benzine or 

 turpentine is not used in the cell. Any cement will do. 

 The cover is of ordinary plate glass but loose on the cell. 

 It has a minute hole drilled in it near the bottom of the 

 cell to form a communication for the water in the body 

 of the cell to the cover of the object. This is an ordi- 

 nary round cover placed upon the plate glass atid with 

 the water containing the BacillariacesB in it. 



To use the growing cell it is placed on the stage of the 

 microscope, which is inclined at the ordinary angle. 

 Then the object, as the Bacillaria, is viewed with the 

 objective. As the water evaporates around the cover, a 

 space of air accumulates in the upper part of the grow- 

 ing cell and water must be added to make it up. This 

 can be done by moving the upper plate glass having the 

 object on it to one side. With this contrivance I have 

 kept Bacillariacese under observation for a long time, a 

 week or more. But I do not see why it cannot be kept 

 in operation indefinitely. As the water evi'.porates of 

 course it must be supplied, or it may have salt water 

 added until it becomes Salter and salter and at last it 

 may become brine and Bacillariacese, or in fact any ob- 

 ject may be observed growing in water from ordinary 

 fresh water to brine. I have in this manner made some 

 interesting experiments which I will detail hereafter. 



Lately I have been experimenting with the growing 

 cell and wanting something that is better, or rather that 

 does not require removal by sliding off the upj^er plate 

 glass to introduce new water, as salt water. To observe 

 the actions of the change of water from fresh to salt on 

 Bacillariacese, I have used the following contrivance. 

 This I find better still than my growing cell, which has 

 but two joints whilst Smith's has six. I use a bottle of 

 two or four drachms capacity. It has fiat sides so that 

 the upper plate glass is done away with and a small hole 

 is bored in it to let the water communicate with the in- 



