even inflow and an even distribution of same is assured through installation of a nuinber 

 of faucets, or through the insertion of a distribution plate. The frames should not be 

 deeper than about 15 centimeters and not wider than from 30 to ^iO centimeters, in order 

 to assure a good view of the eggs at all times. On the other hand, one should not go 

 below a certain minimum size of these baskets. Wilier has shown that a small volume and 

 a small amount of water interfere somewhat with the growth of the embryos in the eggs 

 (excretion factor, mentioned before). The surface size of the baskets greatly influences 

 the growth of the alevins (outflow factor). It was found that brood from a basket of 

 1925 square centimeters, one hundred forty days after fertilization had grown to 25.02 

 millimeters in length, weighing 112,4 milligrams. On the other hand, brood from a basket 

 of only 565,5 square centimeters of size was only 24. .47 .millimeters in length and weighed 

 only 111.2 milligrams. 



If feeding of the brood is intended in the basket (the "understream" basket is less 

 adapted for it than the "longstream" apparatus), the suspended removable sieve is taken 

 out and a smaller otherwise similar sieve is suspended before the outflow. The inner 

 side of the sieve is best painted white (to facilitate the view), and all the rest can be 

 kept black. Special waterproof, quick drying paints for incubators may be gotten fixjm 

 G. Korn (O.K. Farben) in li*esden. Wooden parts are best painted with tarj asphalt 

 lacquer is Just as good but dries very slowly. All zinc parts must be especially well 

 painted over as they will otherwise bring about highly toxic zinc combinations (chloride 

 of zinc, etc.). The inserted sieves can be easily darkened with well-fitting lids. 



On account of the shortness of the undercurrent incubator, several boxes are mostly 

 placed under each other. For this purpose a relatively large fall is necessary, or there 

 must be a very long inflow channel, in order to accomodate the installation of a larger 

 number of boxes. Too many boxes must not be placed under each other, or else the fresh 

 water supply to the lower boxes will be insufficient, and the amount of water to be run 

 through Tdll become too large. It is better to fonn the front wall of the sieve box into 

 a protective sieve, rather than to suspend or insert special protective sieves which 

 mostly do not shut off safely. 



Egg losses during the incubation are essentially determined by the kind of support, 

 that is, by the sieve surface of the insertion. The sieve surfaces used in individual 

 establishments vary greatly. In order to determine the suitability of individual sieve 

 types, I have conducted experiments in the hatchery of the Forestry School at Eberswalde, 

 iqjon wnite metal (tin) sieves with slits (2 x 20 am.), round perforations (2mm. diameter. 

 Fig. 13), wire screen (1.3 x 1.3 nm. mesh, 0.5 mm. wire diameter), and round rods (10 mm, 

 diameter, 2 mm. separations). The results shown in Table 16 were obtained by covering 

 the sieves with single layers of rainbow and brook trout eggs. 



Table 16. 

 The influence of different frame materials upon the loss of trout eggs. 



Year Species Brood stage 



Number of 



eggs per 



frame 



40x40 



Losses in percent 



Wood 

 Rods 



TB-re 



White White 

 metal metal 

 (slits) (holes) 



Passage space of frames: 16^ 575? 28.8^ 40.0$ 



UO 



