The Composition of the Blood of the Shore Crab, Carcinus Moenas Pennant, in Relation to Sex and Body Size

Abstract

1. The influence of body size and sex on the total osmotic pressure (O.P.) and blood conductivity of the shore crab was investigated. 2. In both sexes the O.P. fell steadily as body weight increased. 3. At any body weight the O.P. of the blood of male crabs was significantly higher that that of females. 4. Blood conductivity increased in both sexes until a maximum was reached at a weight of about 35 g. Thereafter the conductivity fell as the weight increased. 5. There was no significant difference in blood conductivity between male and female crabs below 35 g. body weight. Above 35 g. the conductivity of males was significantly higher than that of females.