DEPARTMENT OF MARINE BIOLOGY. 207 



(2) The water-content of different parts of the body is practically iden- 

 tical. This seems to indicate homogeneity of chemical make-up of the body, 

 which in turn shows a low degree of chemical differentiation, despite the fact 

 of a high morphological differentiation of the different parts of the body. 



(3) The relative weight of the three different parts of the body varies 

 according to the absolute weight of the Cassiopea. In other words, these 

 different parts show dissimilar rates of growth, and it is hoped to find some 

 suitable mathematical formula representing the growth curves of these parts 

 to assist us not only in studying the phases of growth, but in comparing the 

 results obtained for the normal with those of the starved Cassiopea. 



(4) Cassiopeas starved for 21 days showed a reduction of body-weight 

 from 62 per cent to 80 per cent, so that the resulting weights were only from 

 38 per cent to 20 per cent of the original. In general, the smaller Cassiopea 

 lost relatively a much greater amount of weight than did the larger animal. 

 In the starved Cassiopea the relative weights of the three parts coincides 

 with those given by the normal Cassiopea, which has a body-weight similar 

 to the starved Cassiopea at the end of the test, and not to the relative weights 

 at the beginning of the experiment. This is highly interesting, since the 

 starved Cassiopea by some process of readjustment seems thus capable of 

 maintaining proportional weights which are normal for its absolute weight 

 at any time. So far as the percentage of water in the different parts is con- 

 cerned, the starved Cassiopea, like the normal animal, shows a like percent- 

 age in all three parts. 



The dried materials obtained from these normal and starved Cassiopea 

 are to be further analyzed in the near future. 



Experiments with Tortugas Sea-water, by J. F. McClendon. 



The true alkalinit}' of sea-water is expressed as PH ( — log hydrogen-ion 

 concentration). The PH of sea-water within 8 miles of Loggerhead Key, 

 from the surface to a depth of 35 meters, varies from 8.1 to 8.22. The CO2 

 tension of this sea-water is about 0.04 per cent of an atmosphere. A con- 

 version table was made, from which the CO2 tension and the total CO2 con- 

 tent of the sea-water may be read after the PH and temperature are deter- 

 mined. Tubes colored Avith thymolsulphonephthalein were standardized by 

 the hydrogen electrode, so that the PH of sea-water may be determined by 

 the simple addition of this indicator, which can be easily done aboard ship 

 in any kind of weather. These tubes show the true alkalinity, the CO2 

 tension, and the total CO2 content of the sea-water simultaneously. Sea- 

 water was titrated with acid, using the hydrogen electrode as indicator, and 

 the results agree with those of Dole's titrations "after boiling." 



Distilled v/ater requires at least 72 hours' aeration before it can be suc- 

 cessfully used in making artificial sea-water; hence the substitution of rain- 

 water is recommended. A close imitation of Tortugas sea-water may be 

 prepared as follows (Steiger's analysis) : 



From 1 nonnal solutions. From isotonic .solutions. 



1,000.00 1,000.0 



