262 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



most suitable temperature is 5° C. [4° Eeaumur or41o F.], ami it should 

 not exceed 10"^ C. [50° F.]. The two extremes of temperature are marked 

 in red on the thermometers furnished to the employees. If the water in 

 the apparatus exceeds the maximum tem^ierature, care should be taken 

 to reduce it to a suitable degree by increasing the quantity of ice in the 

 ice-box. 



Hcigbl, in c iitiiiieters [7.48 inchesl ; breadth at reck, 21 centirnfters [8.27 inches] ; breadth of body 

 of appunifiis. ;;S ccutimotoi-.'? [14.90 inches]. 



A, hiiudlf for carrying tlio apparatus ; B, reservoir for the ice ; b, cover of tliis reservoir ; C, spoiit- 

 for attaching rubber tube (by Towering this tube ruore or loss, the water flows more or leas rapidly from 

 the apparatus) ; d, hook for holding up the tube. 



It might happen that during transportation a solution of continuity 

 might occur in the column of mercury in the thermometer. In this case 

 the mercury should be reduced to its normal condition, by takiug the 

 instrument in one hand and pressing it, or by attaching it to a string 

 and making it describe a rapid circular movement. 



Aerating the icatcr. — The respiration of the young fish vitiates the 

 water in the vessels containing them. The renewal of oxygen is indis- 

 ])ensablc for keeping the fish in good health ; and to neglect this would 

 be to expose these young organisms to certain death. The air should 

 be renewed at short intervals. Although this operation is necessaiy in 

 all kinds of weather, it should be more frequent on very hot days; dur- 

 ing the moments of rest the aerating pumps should be worked inces- 

 santly. 



Nearly all authors are of opinion that during transportation the jolt- 

 ing of the vehicle is sufficient to aerate the water, but this is a mistake. 

 As was shown at the transportation of young fish in 1884, it is very 

 dangerous to count on the agitation of the water for obtaining aeration. 



