Tbriu ' at this time probably the oxygen within the swimbladder (which in 

 the sardine is connected to the cecum of the stomach by a ductus pneumati- 

 cus) or the oxygen produced by the breakdown of the tissues is consumed. 

 Soon there are several spasms of the eyeballs, pectoral fins, and ventral 

 fins in th~t <^rder, ^ro-: ' - frcrr the h^ad toward the tail, and the 

 fish is finally completely dead A peculiarity of the rigor mortis of 

 the dead fish is that ordinarily those which have their mouths open 

 are somewhat, more numerous than those which have them closed, however, 

 there is no such interesting relationship as that seen in Hypomesus 

 olidus during the spawning season, when the males die with their mouths 

 open and the females die with theirs shut* 7 ) 



The lethal levels of free oxygen determined by this method for 

 sardines and anchovies are shown in the following tables. As can be 

 seen from these tables, the values for the lethal level of free oxygen 

 differ more markedly as between individuals than in relation to the water 

 temperature at the time of the experiment „ For Sardinia melanosticta 

 the lowest value per liter was 1„20 cc, and the highest was 2„92 cc. For 

 Engraulis japonicus the lowest was 1.24 cc and the highest was 2,77 cc. 

 However, if these are averaged the lethal quantity for the sardine is 

 about 2 cc per liter, which can be seen to be somewhat lower in the case 

 of the anchovy. This means that if water circulation in the bait well 

 is carried on so that there will be at all times a free oxygen content of 

 3 cc or more per liter, the lives of the bait fish can be absolutely 

 guaranteed as regards oxygen deficiency „ 



When we come to a discussion of the consumption of free oxygen in 

 respiration, we naturally have to take into consideration the increase 

 in carbonic acid gas, but in brief experiments like those described 

 above the accumulation of carbonic acid gas has far less ill effects on 

 the organism than nas the rapid diminution of oxygen,, Even supposing 

 that the operation took place over a long period of time, in a bait 

 tank with a plentiful circulation of water it would be absolutely impos- 

 sible for the accumulation of carbonic acid to cause the death of bait 

 fish. For this reason it was decided to leave for another time the 

 performing of experiments on the effect of the accumulation of carbonic 

 acid gas on bait fish„ 



c) Comparative studies of the capabilities of the new and old types of 

 bait tanks in regard to free oxygen deficiency 



The amount of water is greater in the new-style bait tank, in 

 which the water is circulated positively by a pump, than in the type 

 used hitherto, where the only water circulation is that supplied by the 

 movements of the hull. It can be affirmed on the basis of the reports 

 of this Station that in the future the number of bait fish that can be 

 held will be doubled with little danger of a deficiency of free oxygen, 

 however, the author wishes, in this section, to report the results of 

 further experiments to show how superior the capabilities of the new- 



15 



