SCOTT, STUDY OF CHANGES IN MUSTELUS CANIS 41 



Carcharias — Corpuscles laked in 0.8 per cent NaCl and 0.6 per cent 

 NaCl + urea. 



It is of interest to note that the A of the 0.8 per cent NaCl solution is 

 0.50% while that of the 0.6 per cent NaCl + urea solution is 0.56° ; that 

 is, the molecular concentrations of the two are quite similar. The A of 

 the 0.6 per cent NaCl solution is 0.39° and that of the 0.4 per cent 

 NaCl + urea solution is 0.38°. In other words, the osmotic pressures of 

 the two solutions which first cause laking are in each case similar. The 

 urea in the second set of solutions merely raises the osmotic pressure to 

 the osmotic pressures of the solutions of NaCl. It must be concluded 

 that, since the urea takes the place of the NaCl in these dilute solutions, 

 at least neither the NaCl nor the urea exerts any specific chemical effect 

 upon the corpuscles. The fact that such a great reduction in the osmotic 

 pressure of the external medium is necessary before the haemolysis of 

 elasmobranch blood shows that the integrity of the corpuscle does not 

 depend upon the equality of osmotic pressures between corpuscle and 

 plasma. The corpuscles maintain their integrity even though there is a 

 fall of over 40 per cent in the osmotic pressure of the surrounding 

 medium. We have seen above that Mosso concluded that the resistance 

 of the erythrocytes of the blood varied in a general way with the salt con- 

 tent of the blood. Since the blood of marine teleosts contains very much 

 less salt than that of elasmobranchs, we should expect that teleost cor- 

 puscles would be much more resistant than those of elasmobranchs. 

 Mosso found this to be true of the teleosts studied by him. My results 

 differ in some respects from those of Mosso. The teleosts studied by me 

 show but a small increase in the resistance of their corpuscles over that of 

 the elasmobranchs which I examined. This is shown by the following 

 results : 



Experiment 5. Weakfish, Cyonoscion regalis. Female. 30 inches long. 



No laking in 2.0 per cent NaCl to 0.8 per cent NaCl. Laking decided in 



0.6 per cent NaCl. 

 Female. 20 inches long. 

 Same results as above. 

 Experiment 6, Scup, Stenotonus chrysops. 8 Inches long. 



No laking in 2.0 per cent NaCl to 0.8 per cent NaCl. Distinct in 0.6 per 

 cent NaCl. Decided in 0.4 per cent NaCl. 

 Experiment 7. Killifish, Fundulus heteroclitus. About twenty specimens used. 

 No laking in 2.0 per cent NaCl to 0.8 per cent NaCl. Laked in 0.6 per 

 cent NaCl. 

 Experiment 8. Flounder, Pleuronecies. Female. 15 inches long. 



No laking in 2.0 per cent to 0.8 per cent NaCl. Faint in 0.6 per cent NaCl. 

 Distinct in 0.4 per cent NaCl. 



