allow to get hold of 5 or 6 eggs at a time. The average losses — from good 

 eggs — are about 5 percent but will be as high as 20 percent in the case 

 of rainbow trout. Too great losses make the work unprofitable and the 

 whole crop of eggs may as well be dumped. 



(2) Eggs as well as newly hatched brood has to be protected against light. 

 Exposure to dazzling sunlight is liable — from my own observations — to 

 kill off the eggs. According to Haempel and Lechler. freshly fertilized 

 eggs are verj' sensitive to ultra-violet rays, eyed egss somewhat less. 

 The sensitiveness varies with the different trout species and varieties. 

 Moderate exposure to these rays is said to be beneficial but will provoke 

 premature hatching. 



(3) The oxygen content of the water, used in incubation is to be kept as high 

 as possible. Experiments by TTiller and his co-operators have shown that 

 eggs in water, rich in oxygen (under otherwise l±ke conditions) and if 

 kept in darkness will produce a feeding brood by 58.7 percent greater in 

 length and by 21.5 percent heavier than those that were kept in water of 

 66 percent less oxygen and were exposed to light. Care must be taken 

 that the screens, upon which the eggs rest, are bent downward so as to 

 prevent the occurrence of air bubbles. 



(A) Accumulating mud or slime is to be removed by slowly raising and lowering 

 the screens in the water. After the e^re spots have become visible, this 

 can also be done by raising the screens out of the water and douse the 

 slijne off with a sprinkling can. Altogether, great care is to be taken to 

 keep the water free from dirt particles and — ^worse still — dissolved im- 

 purities. 



(5) Only moderate movements of the eggs are permissible until the develop- 

 ment of the eye spots and they must not be shaken violently. Prcm 

 experiments by Hein. it can be presumed, though, that pressure, blows and 

 falls do not injure the eggs as greatly as was previously assumed. The 

 eggs are least resistant during the second fifth of the incubation period 

 and very resistant during the fourth fifth of the period. 



Tfork connected with the "Zuger Glass" and with the von dem Borne incubation apparatus 

 consists chiefly in the regulation of the through-flow, the maintenance of the filters and 

 the sorting out of the eggs. The tem "self-sorting" (of these apparatus) is really mis- 

 leading. Died-off eggs are not automatically eliminated by the water flowing through 

 the apparatus. Only when the loss of eggs is less than 33 percent can the results of this 

 method of incubation be considered satisfactory. The sorting-out is best undertaken after 

 the appearance of the eje spots. Bad egrs are sucked out with a hose and any good eggs, 

 adhering to them are put back into the water, but should be touched as little as possible. 



The eggs will stand shipping, as soon as they are clearly eyed (Figs. 30 and 3A), 

 but this must be terminated 5 daj-s before hatching in order to avoid greater losses, irtiich 

 are unavoidable if the shipping is delaj-ed. Small amounts of eggs can very well be shipp- 

 ed in thermos bottle or packed in moist moss. Large consignments of eggs are usually 

 shipped in "frames". Such shipments can stand from 2 to 3 days more of transport without 

 any great injuries. The "frames" were recently standardized by the German Trout Breeders 

 Association, 



The "frames" — in shape similar to picture frames — consist of wooden moldings, 6 

 millimeters thick and 20 millimeters wide and are joined together to form a frame of 22 

 by 32 centimeters. One side of the frame is then spanned with cheese cloth or some 

 similar fabric. A thickness of the moldings of less than 6 millimeters may injure the 

 eggs which are often over 5 millimeters in diameter. 



U7 



