On Changes in the Sea and Their Relation to Organisms. 249 



strict comparison between different species in this I'egard, and therefore 

 the comparison is very crude. The cubic centimeters of O2 per hour 

 per kilogram of body- weight and per kilogram of organic matter ( = dry 

 weight — weight of salts in equal volume of sea- water) at 20° is given 

 in table 23. The agreement is about as close as could be expected. 



Vernon has compared the metabolism (per unit weight of organic 

 matter) of jelly-fish, molluscs, tunicates, and vertebrates, and shown it 

 to be remarkably constant. Krogh (omitting jelly-fish, but including 

 eggs and insects) obtained the greatest differences when the total 

 body-weights were used, but the differences probably do not exceed the 

 differences in water-content and in muscular activity. He found the 

 metabolism of a young dog with body-temperature lowered to 20° 

 during the experiment to be greater than that of cold-blooded animals 

 at the same temperature; but if we calculate the metabolism of the 

 average dog for 20°, using a reasonably high temperature coefficient, 

 the agreement is more satisfactory. We should not expect close agree- 

 ment unless water and mineral salts and fibrous tissue are excluded 

 from the weight and the activity of the nervous system is abolished. 

 The chief factor in lowering the metabolism of hibernating mammals 

 is probably the fall in body-temperature (the body-temperature may be 

 as low as 6°). 



It seems probable that the chief distinction in the calorimetry of 

 warm-blooded and cold-blooded animals is in insulation (sensitivity 

 to cold being the regulating factor). All warm-blooded animals are 

 air-breathing, and air brings much oxygen and takes away little heat. 

 The center of a cluster of bees in winter may be 40° above that of the 

 air bathing it. 



The heat-production in a 100-gram cassiopea at 30° is sufficient 

 to raise its body-temperature 0.14° per hour above that of the sur- 

 rounding water, but no such difference in temperature has been 

 observed, because the heat generated is conducted away by the water 

 bringing the oxygen. I found that a fish weighing 1.4 grams used 

 0.825 c.c. O2 per hour at 30°, which is sufficient to raise its body- 

 temperature about 3° per hour, but during this time it was required 

 to breathe 400 c.c. of sea- water, even though it removed half of the 

 oxygen from water saturated with air at this temperature. The water 

 circulating through the gills could remove the heat generated if the 

 body-temperature were 0.01° above that of the water. Since the fish 

 probably removed much less than half the oxygen from the water in one 

 passage through the gills, the body-temperature was probably much 

 less than 0.01° above that of the water. Rogers and Lewis could detect 

 no difference between the body-temperature of fish, salamanders, 

 clams, and earthworms and the water in the thermostat in which they 

 were placed, after they had been in the thermostat long enough for 

 equilibrium. They used a thermo-couple, and one division of the gal- 

 vanometer scale corresponded to 0.0042°. 



