1892. J NEW-YORK MICROSCOPICAL SOCIETY. 9 



to the wants of the investigator of the future, whether in one field 

 or another. For our present purposes, however, it may be good 

 enough, and if we apply the test which it furnishes to our little 

 diatom, we shall find that we have under consideration a really liv- 

 ing thing. 



This conclusion of course assumes that the diatom possesses, 

 in addition to the hard framework or shell, of which I have al- 

 ready spoken, a body of plastic substance called protoplasm. 

 This, upon close examination, we easily learn to be the case. Very 

 simple methods of investigation show that every frustule (as each 

 individual cell is called) is in reality a glass box enclosing a semi- 

 fluid, nearly transparent, but somewhat granular material, con- 

 taining, besides the oily-looking spots or vacuoles to which I have 

 before referred, more or less of a yellowish or brownish-green 

 substance, which gives its general color to the whole organism. 

 There is reason to believe that the semi-fluid material also forms 

 an^enveloping layer on the outside of the siliceous carapace of all 

 diatoms, and in many instances a similar glycerin-like matter per- 

 manently encloses a whole colony of otherwise separate frustules, 

 which passively spend their existence within its restraining grasp. 

 Now, chemical tests disclose the fact that the colloidal mass with- 

 in the transparent valves is composed of carbon, oxygen, hydro- 

 gen, and nitrogen in proportions and relations which characterize 

 an organic substance, and a great number of converging facts, 

 derived from long-continued observation, go to prove that this 

 substance is the seat of all the changes, chemical and physical, 

 which constitute what Dr. Drysdale calls the " interaction of proto- 

 plasm with the environment." In other words, it is the consump- 

 tion and regeneration of this substance "in co-operation with 

 ■external conditions, pabulum and stimuli," which make up the 

 sum of phenomena embraced in this humble creature's life-history. 

 We therefore conclude that this substance is protoplasm. 



It is through and by this protoplasm that the diatom responds 

 to the influences of heat and light, that it receives and assimilates 

 its food, that it moves from place to place as we have seen the 

 boat-like specimen in the Croton water doing, that it grows and 

 reproduces its kind. It was because of its agency in these 

 matters that Prof. Huxley called protoplasm " the physical basis 

 of life," though its name really means " primary formative 



