YELLOW-BROWN CELLS OF CONVOLUTA PARADOXA. 445 
pyrenoid sharply defined. After a further period, however, 
the green cells gradually disintegrated, and the attempt to 
effect what, if it had succeeded, would have been a synthesis 
of no small interest proved abortive. 
Section I1].—THr Yrttow-srown CELLS. 
(a) Description.—In every specimen of C. paradoxa 
taken from the sea yellow-brown cells are present (Pl. 26, 
figs. 5and 6; Pl. 27, figs. 7, 8,and 9). These cells are as con- 
stantly characteristic of C. paradoxa as are the green cells 
of C. roscoffensis. Though not so numerous as to give, 
when examined microscopically, the appearance of a continuous 
tissue as is the case with the green cells of C. roscoffensis, 
the yellow-brown cells of C. paradoxa are, nevertheless, 
present in the adult body in great numbers. ‘They occur in 
groups or rows situated for the most part just beneath the 
epidermis, though they also occur in the deeper tissues. The 
number of yellow-brown cells increases with the size of the 
animal. Very minute young specimens contain but few, mid- 
sized animals more, and adults most. ‘This increase is effected 
in part, at all events, by the division of the yellow-brown 
cells (Pl. 28, fig. 18). When examined in the living state, 
soon after the capture of the animal, each yellow-brown cell 
is seen to contain many irregularly oval or polygonal, yellow- 
brown discs which occupy the greater part of the cell. Lying 
about the margin are a number of more elongated, browner, 
somewhat boat-shaped bodies. The remainder of the cell 
consists of one or more clear, transparent, vacuolar areas ; 
occasionally, colourless, rounded refractive bodies also occur 
(CA Bae sales Che 
But if the microscopic examination is made immediately 
after the animals have been caught, the yellow-brown cells 
are seen to differ markedly from those of animals kept for an 
hour or so before examination. Most of the yellow-brown 
cells in the just-caught specimens have a large colourless, 
transparent, anterior region, which may be as much as half 
