Osmotic Relationships in Opheodesoma spectabilis — Freeman 
65 
this mixture, while the animal is continually ex- 
truding pellets free of any vegetable matter. 
However, animals can vary markedly in their 
nutritional activity, even when lying side by side. 
Evaluation was made of osmotically active 
substances of fluids from coelomic and tissue 
compartments before and after osmotic stress. 
For coelomic fluid determinations, draining was 
induced and samples were taken. Animals were 
either returned to 100% sea water, as in the 
case of the controls, or were immersed in dilute 
sea water. All animals were kept in tanks for 
24 hr; then draining was repeated and samples 
were taken. Tissue fluid was obtained by drying 
drained animals thoroughly in toweling and then 
macerating them in a Waring blender. The re- 
sulting homogenate was pressed through a fine 
fiberglass mesh and finally filtered. 
Figure 5 shows that the mOsmol values for 
coelomic fluids are slightly lower than for en- 
vironmental water. The low concentration of 
tissue fluid is surprising, if it is assumed that a 
concentration equilibrium usually exists between 
body and environmental fluids in marine inver- 
tebrates. The fact that tissue fluid values are 
nearly the same whether or not sea water was 
diluted in the environment is also difficult to 
explain. It was hypothesized that draining the 
animals in the manner described might be in- 
strumental in removing salt from the tissues. To 
test this possibility, coelomic fluid samples were 
obtained in two different ways from the same 
animal. One method was by draining as usual, 
the other was by aspiration of a small amount of 
fluid directly through the body wall by using a 
needle and syringe. 
The concentrations in samples so obtained are 
compared in Figure 6, both in mOsmols of un- 
specified substances and in /uMols of sodium. 
The significantly higher values of the drained 
GROUP 
Control 
GROUP 
2 
Effect 
of 
dilution 
sodium concentration uMols per milliliter 
D * Coelomic fluids drained 
BW S Coelomic fluids obtained through body wall 
Fig. 6. Comparison of concentration of coelomic fluids obtained in two different ways. Immersion in 100% 
and 80% sea water for 24 hr. 
