#2 SOUTHERN CALIFORNIA ACADEMY OF SCIENCES 
Diatoms 
By Miss Sarah P. Monks. 
Diatoms are organisms that have characteristics of both 
plants and animals. Unlike other plants they have the power 
of voluntary motion, and, unlike most animals, they possess 
ehlorophyll. They are microscopic. 
Zoologists look at them askance and botanists do not want 
them, but they are the pets of the microscopist, and well they 
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Fig. 1. Arachnoidiscus Mag. 300 Diam. 
Micro Photograph by S. J. Keese 
deserve this honor, for they are among the most exquisitely 
beautiful objects of the world. 
They, unlike plants, have a silica shell composed of two 
valves, one fitting over the other like the lid of a pill box. 
These glassy valves are decorated with knobs, points and 
striw, arranged in the most varied and delicate tracery. Some- 
times under a low micro power, diatoms appear changeable, 
blue, green and various colors, because their tiny projections 
break the white hght into its rainbow tints. 
Diatoms are at present, classed as brown alge, or sea weeds, 
on account of the dark brown pigment under their siliceous 
shell. 
An interesting fact in regard to color was noticed by the 
Russian diatomologist, C. Mereschowsky, among the recent 
