152 THE AMERICAN MONTHLY [Juu 



books about them only as dead shells, the Diatoms in fact. 

 But as we are going to get them living as Bacillaria, we 

 are also going to procure them as dead shells, (Diatoms). 

 DiatomacefB were supposed to be vegetables, the relics of 

 the "animalcules" of all the older naturalists. Diatoms 

 in common parlance is the term used for the prepared 

 shells of DiatomacesB. Bacillaria are what are known as 

 Protista, that is to say organisms which occupy a place 

 in nature, as described by man, between the animal and 

 the vegetable. 



The Bacillaria are minute and seemingly unicellular, 

 having but one cavity. But the cell contents are divided 

 into two sections. However, they are taken as one-celled 

 or unicellular organisms. Begining at the outside they 

 are made up of an extremely thin coat of a substance 

 which has not been analyzed as yet, but seems to be pro- 

 toplasm. Then comes the shell or lorica. This is com- 

 posed of hard matter which is very soluble in fresh-water 

 and sometimes contains silica or aluminium silicate. When 

 they are cleaned or when found as fossils in the earth, the 

 matter is siliceous, like clay, and this is what is known 

 as Diatom, so that diatoms are the shells of Bacillaria. 

 We talk about hunting for dead diatoms or for living Ba- 

 cillaria. 



Within the shell are the cell contents, which have not 

 been analyzed as yet. But the main mass consists of large 

 quantities of endochrome. This is olive-colored matter 

 and can be distinguished when the Bacillaria are viewed 

 with the unassisted eye. The conferva) are bright green 

 water plants but the Bacillaria are yellowish. When view- 

 ed by means of the microscope the endochrome is seen to 

 occupy the outside of the cell contents but within the 

 shell it occupies two portions one of which is situated on 

 the inside of each valve. In Spring, in this climate, when 

 the Bacillaria appear they have an endochrome, and it is 

 scattered over the inside of the endochrome plates, — 



