1888.] Messrs Haycraft and Carlier on Invertehrate Blood. 425 
nipping off one of the smaller claws. The crab was then held over 
castor oil, and the blood allowed to fall into it. Contact of the 
blood with the sides of the vessel was prevented by frequently in- 
' verting it. In some fifty experiments done in this way the blood 
clotted rapidly in all but one case. We were not discouraged, how- 
ever, but believed that our want of success was due to the blood 
coming momentarily in contact with the crab’s tissues before falling 
into the oil. 
It seemed impossible to avoid this, and we determined to select a 
more suitable animal. 
We trephined the interambulacral areas of an echinus, and drew 
out the blood (coelomic fluid) with a pipette, which had been pre- 
viously immersed in castor oil. In this way contact of the blood 
with the tissues of the animal was avoided. 
The blood so obtained remained in most cases — about twenty in 
aU-— perfectly fluid in the oil for periods ^of from thirty to forty 
minutes. We never prolonged our experiments beyond that time, 
owing to the necessity of constantly reversing the jar at short inter- 
vals, which required great' care and attention. The blood of the sea- 
urchin varies very much in the number of corpuscles present in the 
different specimens. In most cases, when allowed to coagulate, the 
clot is very small, and not easy to demonstrate in a few drops of 
blood. 
We turned our attention again to the crab. This time the animal 
was held up by one of its great claws, which caused the blood to 
gravitate into the remainder of its body. The tough membrane 
covering in the larger joints of the claw was then cut away, and an 
oiled pipette introduced through the wound into the large joint 
sinus. By lowering the claw to the general level of the body, and 
by the application of slight suction to the end of the pipette, a 
sufficient quantity of blood was easily obtained. This was trans- 
ferred to castor oil. 
Crab’s blood, when shed, clots in about five minutes, when the 
opaque, pinkish fluid becomes water-clear, with a branching clot 
within it. During and after coagulation the clot becomes of a 
brown-black colour from the development within the corpuscles of 
a pigment. 
Within the oil the blood remained for as long as we examined it 
