180 How to obtain it. 



bear removal they were placed on fresh grilles, whilst the others 

 were being dried and re-varnished, ready for further use. Apart 

 from accidental scratches, which let in the water, it will percolate 

 through and corrode the metal, and wherever this corrosion takes 

 place the eggs suffer. One very weak point I have found to be the 

 place where the wires enter the wooden frame. At this point it is 

 often difficult to prevent corrosion taking place during the period 

 of incubation, and, wherever it does take place, there it causes 

 injury to the delicate embryos. It may not kill them at once, but 

 it weakens them so that they cannot live to grow up. 



Livingstone Stone says " Fourteen trout eggs were placed 

 on a copper-wire screen in November, 1869, at the Cold Spring 

 Trout Ponds, and in fifty days they had absorbed so much copper 

 that they were of a dark brown tinge and hard like peas." Many 

 of my correspondents have found metallic trays, chiefly zinc, very 

 hurtful indeed to the ova. 



It is better to work with fewer eggs, and to do the work well, 

 than to go in for large numbers ; and I would hand on this piece 

 of advice to all who contemplate having anything to do with the 

 incubation of ova. It is the key to the whole work, and any point 

 overlooked, however trivial it may appear at the time, may cause 

 wreck and ruin afterwards. The preparation and incubation off 

 the ova is a special work, requiring much care and attention, and 

 can only be successfully done by those who thoroughly understand 

 it. The hatching of ova, after having been properly prepared and 

 incubated, is a very simple matter indeed, and can be done by 

 any man of ordinary intelligence. So simple and easy has it been 

 made, indeed, that the eggs, as already explained, will hatch them- 

 selves, if placed in a well-made artificial hatching bed. It is here 

 that we gain considerably on Nature. Nearly all the loss which 

 takes place in the egg stage is prevented. 



Loss has been variously estimated by different specialists, but 

 we are not far from the mark in assuming that a very small per- 

 centage, indeed, of the eggs naturally deposited in our streams live 

 to produce mature fish. The number probably varies a good deal 

 according to circumstances, but we know that in many cases not 

 one -egg in a thousand survives. Whole spawning beds are some- 

 i times washed away, and the contents destroyed. The host of 



