YELLOW-BROWN CELLS OF CONVOLUTA PARADOXA, 4059 
indeed, all those belonging to the chosen race of yellow- 
brown alge, but only those that can withstand digestion. 
How some possess this power, or acquire it, may lke- 
wise be imagined. When, as often happens, the body of C. 
paradoxa is gorged with solid food—in one case upwards of 
70 diatoms were counted in a single animal—the activity 
directed toward the digestion of any single cell is lhkely to 
be reduced. Thus, it may be that the glut of solid or reserve 
food in the body may act temporarily as a protection to the 
yellow-brown cells. Profiting by this respite, the algal cells 
may react adaptively by change in osmotic power, or in 
permeability of plasmatic membrane, and so prepare to 
resist the action of the normal digestive juice of the animal. 
By what chemical mechanism the animal cells come to tolerate 
the presence of these foreign cells, or by what means the 
fatty reserves are discharged from the algal cells, it is im- 
possible to say. An investigation of the proteases and other 
enzymes of C. paradoxa, particularly with a view to deter- 
mine in what medium they act, might throw some light on 
the enigma of what maintains the balance between foreign 
algal cell and animal so equipoised that the former behaves 
like an integral part of the latter. To discuss such questions 
in the present state of our knowledge of invertebrate physio- 
logy, though tempting, is vain. 
Apart, then, from all theoretical considerations, experi- 
mental proof is forthcoming that the eggs of C. paradoxa 
contain no yellow-brown cells; that larve, unless exposed to 
the weed of the Paradoxa zone, remain uninfected, and that 
infection may be induced by bringing the recently hatched 
animals into contact with this weed. Thus, except for the 
fact that it is much more uncertain in C. paradoxa, there is 
with respect to infection a complete agreement between C. 
paradoxa and C, roscoffensis. Both animals require to be 
reinfected in each succeeding generation. In neither is there 
any transmission of infecting organism from one generation 
to the next. 
The greater certainty of infection of C. roscoffensis 
