YELLOW-BROWN CELLS OF CONVOLUTA PARADOXA. 449 
with iodine. Hence the colour-reaction obtained by Haeckel 
and Miller may well have been due to the presence of 
carotin, and not to the presence of starch. 
Again, Brandt’s hollow starch grains—fine granules sur- 
rounding a vacuole—suggest, though somewhat remotely, a 
degenerated pyrenoid with its starch sheath. Third, the red- 
violet granules described by Brandt cannot be regarded, merely 
because they increase in numbers in bright light, as of the 
nature of photosynthetic products. It is at least as likely 
that they owe their origin to a light-induced modification of 
carotin or some similar pigment. 
In any case accurate information as to the nature of the 
assimilate of the Zooxanthelle is lacking, and it is to be 
hoped that those engaged in researches on the Radiolaria 
will clear up this matter. 
(c) The Reserve-fat of the Yellow-brown Cells.— 
The yellow-brown cells of C. paradoxa contain no starch ; 
but reference has already been made to the occurrence, in the 
yellow-brown cells of animals examined immediately after 
capture, of refractive globules. These droplets (PI. 27, fig. 8) 
lie apart from the chloroplasts in the colourless reticulum 
of the cell. The substance composing them is soluble in abso- 
lute alcohol, stains a grey or brownish colour with osmic acid, 
and gives the yellow-red fat-reaction with Sudan III. The 
osmic reaction is somewhat faint till after the preparation has 
been treated with alcohol, when the brown coloration of the 
globules gives place to black. ‘This behaviour is, according 
to Bolles Lee (‘ Microtomist’s Vade Mecum,’ p. 36, 1900), 
characteristic of stearin and palmitin, and of the corre- 
sponding fatty acids. It may, therefore, be concluded that 
the refractive droplets of the yellow-brown cells consist of, or 
at least contain a fatty substance. That they are of the 
nature of reserves is. suggested by the facts that they 
disappear gradually from the yellow-brown cells of animals 
kept under the somewhat abnormal conditions obtaining in 
the laboratory, and that this disappearance is more rapid in 
dark-kept animals. 
