452 FREDERICK KEEBLE. 
of a cell of a mammary gland in its active stage. The large, 
clear, anterior end of the yellow-brown cell, only visible in 
fresh caught specimens which by the nature of their habitat 
have just been exposed to high light-intensity, is seen often 
to contain one large oily droplet. In some, one or more 
large droplets are situated in the deeper part of the clear 
anterior end, whilst in others a single large oil-drop lies close 
against its anterior margin, separated only from the animal 
tissue by the finest of membranes. Finally, other large 
globules may be seen lying just outside the colourless 
anterior borders of yellow-brown cells, and presenting every 
appearance of having been extruded from them (PI. 27, 
figs.8 and 9). It is not, of course, suggested that all the fat- 
globules, of which great numbers occur in the body of fresh- 
caught animals, are derived from the algal cells. Doubtless 
some fat comes from the digested solid food, diatoms, foramini- 
fera, copepods, tetraspores, and the like on which C. paradoxa 
feeds so copiously. But it is claimed that the algal cells, 
when actively photosynthesising, regularly pass on the excess 
of their assimilate in the form of fat to the animal tissues. 
These observations throw light on certain others which 
are recorded in the paper on “‘Convoluta roscoffensis” 
(Keeble and Gamble, 1907). Here, in some preparations, 
rows of fatty granules are to be seen passing from the green, 
algal cell to the neighbouring animal cells. It is highly 
probable that this fat represents the translocation-form of the 
ternary substance which C. roscoffensis obtains from its 
contained green cells. In this former paper, where proof 
was given that food-substances do actually pass from the 
green Cells to the animal, it was suggested that the reserve- 
starch of the green cell travelled from that cell to the animal 
tissue in the form of sugar. But, having regard to the 
known fact that in plants starch is very readily converted 
into fat it may well be that the reserve-starch.of the green. 
chlamydomonadine cell of C. roscoffensis undergoes con- 
version into fat before passing out from the algal cell into 
the animal tissues. 
