200 THE AMERICAN MONTHLY [July 



fluid endoplasm. The Diatom is said to contain chloro- 

 phyll or a substance called Diatomin, but when we are 

 studying one of the largest of the Navicula>, we find that 

 the general color of the whole frustule whether seen un- 

 der a power of x600 or xl.200 is some shade of green or 

 brown and that the globules themselves contribute most 

 of the green color, independent of the darker stratified 

 layers along the frustular zones as well shown when the 

 sutural faces are shown in the field. 



Now by comparison (in the relatively short study made 

 for the purposes of this paper), I have incidentally ob- 

 served many species of Infusorians (Protozoa) filled with 

 green globules, commonly regarded as food balls, which 

 are scarcely distinguishable from the greenish globules 

 associated with the contents of the Diatomacese and as the 

 Infusorians whirl, drag or surge along, the green globules 

 tumble or roll about promiscuously or flow in proces- 

 sional streams, or remain in the same place relative to 

 some adjacent organ, and sometimes the most minute 

 Infusorians appear of a brighter green than diatoms 

 ever appear. In an active Navicula major in the double 

 frustular condition, and moving with its sutural sides 

 uppermost, I observed that a brownish and rather dense 

 layer of endochrome rested longitudinally upon and 

 compressed three large diaphanous, colorless globules, 

 between the layer of endochrome and the valvular face 

 of the Diatom. The resistance of these three globules to 

 compression gave the zone of endochrome a wave-like 

 undulation, very striking in its eff"ect, and which had 

 not been previously seen in any previous studies of 

 NavicultT. This special case of the internal contents sug- 

 gests a more complex morphological condition than 

 seems to have been noted heretofore as appertaining to 

 the general contents of the frustule. 



Reverting to appearances observed by Prof. II. L. 

 Smith in relation to the biology of the Diatom, the ma- 



