608 
G. H. DREW. 
Methods. 
Collection and Preservation of Living Animals. 
Cardium norvegicum can be obtained in the neighbour- 
hood of Plymouth by dredging on several grounds at a depth 
of twenty to thirty fathoms. It was formerly quite plentiful, 
but the supply has been falling off somewhat during the last 
few years. The animal will live for many hours out of water, 
and for some days if packed in damp seaweed. I have kept 
a number for months in the Laboratory in basins into which 
a small jet of sea-water flowed. Sufficient food is obtained 
from the minute forms of life present in the water circulating 
in the experimental tanks, and any artiflcial method of 
aeration is unnecessary. The vitality of the animal is so 
great that a relatively large volume of blood may be with- 
drawn, and complete recovery ensue, in the course of a few 
days, after which the blood appears to be normal in consti- 
tuents and quantity. 
Collection of Blood. 
The blood can be most conveniently obtained from the 
anterior adductor muscle. When the valves of the shell are 
slightly apart, a small wedge is introduced between them to 
prevent closing of the shell ; this usually causes the protru- 
sion of the large and powerful foot, which is violently waved 
about, and may displace the wedge unless it has been inserted 
near the anterior adductor muscle, where it is beyond reach 
of the foot. A clean, fine-pointed glass pipette, fitted with 
a rubber teat, is then introduced between the fibres of the 
adductor muscle, and the blood slowly withdrawn. 
The following precautions should be taken : 
The pipette should not be forced through the adductor 
muscle so as to rupture any of the viscera ; it should pene- 
trate about half-way through the muscle, and then be slightly 
withdrawn to free the end. 
