A454 FREDERICK KEEBLE. 
Animals kept for a long period in ordinary filtered sea- 
water, even though they are exposed to the light, become 
ultimately reduced almost to microscopic size. Thus, examples 
put in filtered water (July 24th, 1907) measured (L. 2. 8) 
120 x 83 = 9900. After a month (August 23rd) a specimen 
measured 60 x 30 = 1800, i.e. + of its original size, That 
such small animals as C. paradoxa are able to withstand 
starvation for such long periods points definitely to the con- 
clusion that they are living at the expense of their algal cells. 
Microscopic examination of animals kept in light and dark- 
ness in filtered sea-water shows that, as the animal tissues 
waste, so the yellow-brown cells become more and more 
reduced both in size and numbers. 
That this reduction of the algal cells is more rapid in “dark- 
filtered” than in “light-filtered”’ is seen in the results of the 
experiment already cited, in which, after nine days, the size 
of “light-filtered”’ animals was to that of “ dark-filtered ” as 
2°5:1. At the time these measurements were taken, the 
records for the algal cells in the two cases of lhght-kept and 
dark-kept animals ran thus:—lLight-filtered, number of 
yellow-brown cells double that in dark-filtered. 
Size of yellow-brown cells :—Light-filtered, most 4 divisions 
(ocular micrometer, L. 2.6) = 14°84; some 6 div. = 22°2 p 
and more. Dark-filtered, most 2 div. = 7:4; some 3 div., 
some 5 div. = 185 nu. 
This rapid degeneration of algal cells in animals kept in 
filtered sea-water in the dark offers some means of obtaining 
information as to the nutritive relations which exist between 
yellow-brown cells and animal. For the purpose of this 
enquiry, animals of similar origin were placed in the dark, 
some in filtered sea-water, others in unfiltered sea-water 
with weed rich in food-material (diatoms, etc.) from the 
Paradoxa zone. After nineteen days the number of yellow- 
brown cells was greatly reduced in both. It is true that 
the reduction in numbers and in size had proceeded 
further in the dark-unfiltered than in the weed-fed animal, 
and that, whereas no normal yellow-brown cells were to 
