PHYSIOLOGY OP LAMBLLIBRANCH BLOOD-CORPUSCLES. 613 
invai'iably found that the total salts in the blood was slightly 
less than that in the water in which the animal lived, but his 
published researches do not extend to any species of Cardium. 
The organised elements in the blood of Cardium norve- 
gicum consist entirely of amoebocytes. As seen in the freshly 
drawn blood, they appear as slightly granular, colourless 
corpuscles showing a number of short pseudopodia ; they 
vary considerably in size, but the different varieties of the 
corpuscles cannot be easily distinguished in unstained prepa- 
rations, nor can the nucleus be clearly made out. 
If a slide in which the cover-glass is supported at the 
corners with wax, so as to ensure a fairly thick film of blood, 
be kept under observation, it will be noticed that the cor- 
puscles perform slow amoeboid movements. After the lapse 
of about half an hour many of the corpuscles can be seen fully 
extended, and may then measure three or four times their 
diameter in the contracted state. In this condition they are 
very thin and ti'ansparent, and can be most conveniently 
observed under a nari*ow cone of illumination. The pseudo- 
podia are often remarkably long and slender. 
Stained preparations show that the corpuscles can be 
divided into three classes : 
(1) Finely granular eosinophil corpuscles (fig. 1). These 
are the lai’gest corpuscles present. They possess a single 
round or oval nucleus, and a relatively large amount of proto- 
plasm, which contains a number of exti-etnely small eosinophil 
granules, chiefly concentrated round the nucleus. The longer 
pseudopodia are as a rule free from these granules at their 
extremities, but there is usually a line extending round the 
periphery of the corpuscle, which stains slightly with eosin. 
(2) Coarsely granular eosinophil corpuscles (fig. 2), similar 
to the finely granular variety, but slightly smaller, and 
possessing large, well-defined, eosinophil granules. 
(3) Basophil corpuscles (fig. 3). These are much smaller 
than the two preceding varieties, and do not take on the 
eosin stain at all. They possess a sing’le round nucleus, and 
a very small amount of protoplasm, which also takes on the 
