462 FREDERICK KEEBLE. 
plasts were pressed, whilst in the centre a large number 
(thirteen counted) of irregular, oval, pale yellow-brown 
bodies occurred (Pl. 28, fig. 15a, b, c). These yellow- 
brown structures contained each a central dark spot, and each 
when seen in profile showed the appearance of a vertical cleft — 
extending through about half its depth. The wall by which 
these yellow-brown bodies were enclosed underwent change of 
shape due to the movement of the animal, whence it may be 
assumed that it consisted of animal vacuole-wall together with 
extremely delicate algal cell-wall. During examination the 
vacuole burst, and the contained irregularly oval, pale brown 
bodies were discharged into the body, and lay in groups of 
twos and fours. None of the other vacuoles of the body burst, | 
and so there is a possibility that what was witnessed was the 
liberation of a group of daughter-cells from a mother-cell. 
On this view the peripheral chloroplasts are to be regarded, 
as already suggested, as the partially degenerate chloro- 
plasts of this mother cell and the yellow-brown irregularly 
oval bodies as daughter cells, and not merely as chloroplasts. 
This interpretation of the phenomena finds support from 
facts connected with the development of yellow-brown cells 
in the body both of the larval and adult animal. Thus, in 
the former, besides the large cells described, just infected 
animals not infrequently contain minute yellow or yellow- 
green cells with only three peripherally placed chloroplasts, 
one oval and two somewhat elongated and pointed (Pl. 28, 
fiv.12). Intheadult animal also, beside the large yellow-brown 
cells with numerous chloroplasts, there occur minute yellow 
cells, consisting now of a single, now of several chloroplasts. 
Figures, Pl. 28, figs. 11, 12, 18, 18, represent these various 
stages in the development of the yellow-brown cells of 
larval and adult animals. The paleness of the colour— 
greenish-yellow, grey-yellow, yellow—both of the small cells 
of the adult, and of the irregular, oval structures contained in 
the large, developing cells of just-infected animals supports 
the view that the infecting organism has a-colourless, sapro- 
phytic, free stage as well as a yellow-brown, holophytic, free 
