TEE CHEMISTRY OF MEDUSA 



127 



SESSIONAL PAPER No. 22a 



The physiological habit, established ancestrally, is maintained. Loew's idea that, 

 because potassium salts favour chemical condensation-processes, this accounts for the 

 high selective capacity for potassium possessed by animal and vegetable organisms, 

 fails, however well-founded, and does not explain why medusa cells pack such salts 

 away in the inert or dead jelly of the bell. 



Reference may be made to other salts, small in quantity but important, and con- 

 veniently omitted in estimating the total sum of salts in sea-water and in the juices of 

 medusae. There is apparently no alumina in Aurelia, and Cyanea, while the silica 

 detected is so small in quantity that it may be due to sand particles, protozoan skele- 

 tons, &c., in the gullet and gastro-vascular canals, though the jelly of Aurelia may 

 contain silica, as sponges and coelenterates, of course, can utilize the silica of sea- 

 water. The iron present is, in St. Andrew's Aurelice, -0036 to -004 per cent, and in 

 Canso Aurelice -00087 (volumetrically), while in Canso Cyanea it is '001796 to -00207 

 per cent, whereas St. Andrew's sea-water contains only -00006 per cent and Canso sea- 

 water slightly more, viz. : '00098 per cent. Phosphoric acid in Aurelia juice contains 

 -013314 per cent and Cyanea juice '030315 per cent, but it must be noted that only a 

 small portion exists in inorganic combustion, the rest being from nucleo-proteid and 

 lecithin. Bromine in sea-water, according to the late Professor Dittmar, is '3402 of 

 the total halogen, and in Aurelia from Canso, with a total halogen of 1 '723, it would 

 be '00586 per cent. Iodine, in 50 litres of sea-water, amounted to '0006, yet in con- 

 trast to analyses of sponges, repeated and careful tests with Aurelia and Cyanea^ failed 

 to show the presence of that element. Another method showed its presence, but only 

 'OOOOl to '00025 in 50 litres, and probably minute animals account for it. A very 

 large quantity of the juice is necessary to determine its presence.f Does the gastro- 

 vascular lining (i.e. the epithelial cells) reject iodides in sea-water, just as the sul- 

 phuric acid is rejected? If so, that is the explanation of the much smaller amount of 

 iodine the medusa contains than the sea-water contains, in which it lives. 



The conclusions yielded by the very elaborate and careful analyses of Professor 

 Macallum, and summarised in the final pages of his paper, may be concisely stated as 

 follows : — 



1. Medusae differ in their chemical composition, as regards salinity, from the sea- 

 water in which they live, and two species differ from each other, in the same water and 

 on the same day. Specific individuality is not signalized by morphological and 

 anatomical features only, but is indicated by inorganic chemical composition as well. 



2. The salinity of the sea-water environment may vary considerably, but afiects 

 very inconsiderably the salinity of organisms like medusae. 



3. Salts, once deposited in the jelly of living medusae, are unaffected by osmosis 

 while they continue to live in sea-water. 



4. The sodium in medusae is slightly less, and the potassium considerably more, 

 than in the sea-water, taking the total halogen as the standard. The lime is about the 

 same as in the sea-water, but the magnesia is less (as much as 10 per cent less), and 

 the sulphuric acid very much less (32 to 35 per cent) in the medusae. 



5. The iron is more, and the iodine less, in medusae than in sea-water; and the 

 latter is apparently not associated with any compound which -can be precipitatedl by 

 alcohol. 



6. The lining cells of the medusa's digestive system are living units, which exer- 

 cise selection in absorbing the salts of sea-water, and this selection is more vigorous in 

 respect to some constituents than others. 



* 2 litres of the juice were used. 



tThe total amount of proteid in Aurelia is very small, only '^/h to Vs per cent of its total 

 weight; thus 2,000 oc. of juice only yields a total of 2-6 grains of proteids, 



22—12 



