456 FREDERICK KEEBLE. 
less. Finally, nothing appears to be left of the algal cells, 
but heaps of few or many colourless, curiously persistent, 
granules. The time required for the algal cells to be reduced 
to such granular remnants varies considerably; in some 
experiments it took fourteen days, in others nineteen days or 
longer. 
Experiments were instituted in order to ascertain whether 
the remnants of the yellow-brown cells left in the body after 
prolonged exposure to darkness were capable of regenerating 
into normal yellow-brown cells; but, as an understanding of 
the results obtained requires a knowledge of the appearance 
of the algal cells in their young stages, the results are 
deferred till after this appearance has been described 
(p. 460). It may, however, be mentioned here that, when a 
redevelopment of algal cells was induced in animals which 
had been kept previously for long periods in darkness, the 
animals which, during their sojourn in darkness, had become 
reduced to the size of larvee, began at once to grow again. 
Thus, after fourteen days darkness three animals measured 
superficially in divisions of the ocular micrometer L. 2. 3:— 
10 xX oe — 118 mm,2 71) 43 =.87 mm. sande4. esac 
°37 mm. Average =°8 mm. Whilst animals similarly 
treated but subsequently brought into the light and sup- 
plied with weed, under which conditions algal cells reap- 
peared, measured, after four days exposure to the new 
conditions of light and food, 92 x 55=1:46 mm.; 74 x 54 
— 1:15 mm.; 78 x 40 = ‘9 mm. and 50 x 30 =°5 mm. 
Average 1 mm. 
Though, by reason of original differences in size, too much 
weight cannot be given to individual measurements, the 
phenomenon of apparent increase was so uniform as to 
admit of the conclusion that growth of the animal is bound 
up with the presence of living yellow-brown cells. 
(e) The Origin of the Yellow-brown Cells.—A larval 
Convoluta paradoxa, as it hatches out from its ege- 
capsule, contains no yellow-brown cells nor any precursors 
thereof. OC. paradoxa is in this respect. precisely similar to 
