618 
G. H. GREW. 
contains approximately the same amount of dissolved air as 
the surrounding water. 
The corpuscles also aggdutinate in the case when the 
animal, with the shell-valves wedged open, is washed with 
distilled water, and the blood withdrawn with a dry pipette. 
This disposes of the possibility of agglutination being caused 
by admixture with sea-water. Mixture of the blood with 
hypertonic or hypotonic salt solutions also does not hinder 
agglutination. 
'Phe possibility that some stimulus, conveyed to the corpuscle 
by contact or friction with some foreign body, is the predis- 
posing cause of agglutination, is suggested by the fact that 
corpuscles can be seen to agglutinate after contact with a 
foreign body, and more especially by the fact that the rapidity 
of the change in the corpuscle appears to depend on its 
momentum when impinging on the body. The fact that 
agglutination does not occur so readily after contact with a 
polished surface, such as glass, where there would be less 
friction, is also in favour of this theory. 
Phagocytosis. 
Idle phagocytic action of the corpuscles on bacteria can be 
watched by placing a di’op of blood on a slide, and adding a 
loopful of a culture of bacteria in broth diluted with sea- 
water. Tlie corpuscles can be seen to send out pseudopodia 
in the direction of the bacteria, and engulf them. They may 
then be fixed and stained as before (figs. 5 and 6). Agglu- 
tinated corpuscles do not appear to possess this power, but 
motile bacteria, in the course of their movements, may touch 
and adhere to them; this is probably a purely passive action 
on the part of the corpuscles. No phagocytic action on the 
part of the basophil corpuscles was observed, nor did stained 
preparations show that this had taken place. Experiments 
were tried by introducing capillary tubes containing cultures 
into a di'op of blood under a cover-slip, supported at the 
corners by wax; in this case a certain number of corpuscles 
