PHYSIOLOGY OP LAMELLIBRANCH BLOOD-CORPUSCLES. 615 
of blood. Individual corpuscles can be watched as they near 
the opening, and it will be seen that the majority touch the 
bands of plasticine at least once before they adhere to its 
surface. When the stream of blood is extremely slow, so 
that the momentum of the corpuscles on contact is slight, a 
corpuscle may touch any foi’eign body three or four times 
before adhering, but if the momentum of the corpuscle be 
greater, it may adhere on the first or second contact. In the 
case of contact with a polished surface, such as glass, the 
power of agglutination is not so marked. Once a corpuscle 
has adhered, it possesses the power of sticking to any other 
corpuscles that may come in contact with it, and these, in 
their turn, can then adhere to others. That this power of 
mutual adhesion is not possessed by the corpuscles in the 
freshly drawn blood, is proved by the fact that corpuscles 
may often be seen impinging without showing any tendency 
to adhere, until one of them touches some foreign body, or 
meets with other agglutinated corpuscles. Two corpuscles, 
one or both of which have developed this power of aggluti- 
tion, may frequently adhere to each other by their pseudo- 
podia, and then become separated by the blood-current ; when 
this occurs, a thin protoplasmic connection seems always to 
remain between the corpuscles. 
This phenomenon can best be studied by placing a few 
strands of cotton-wool between the convergent bands of 
plasticine. In this case, the corpuscles can be seen to form 
agglutinated masses along the strands of cotton-wool, and 
frequently thin protoplasmic connections are visible between 
masses of corpuscles situated on different strands of cotton 
(fig. 4). At first these bands may be so thin as to present 
considerable difficulty in resolution, unless oblique illumina- 
tion be employed. Even when invisible, their presence is 
often shown by their power of arresting and adhering to 
passing corpuscles. I have frequently followed the course of 
two corpuscles, which had adhered by their pseudopodia, and 
then become separated in the blood-stream, and settled down 
on neighbouring strands of cotton-wool. In such cases a 
