14 On Stocking. 



are three secrets of incubation, these are : no 

 strong light ; no sudden change of temperature ; no 

 stagnant water. Strong light injures the nervous 

 system ; sudden change of temperature injures 

 the veinous system ; stagnant water injures both. 

 The light can be controlled with a little care ; the 

 even temperature can be insured by incurring some 

 expense. But to render the eggs secure against 

 stagnant water requires both great care and much 

 expense. The hatching trays must be so arranged 

 that a current of water is constantly impinging 

 on each individual ovum and sweeping off (the 

 pores of the shell) the carbonic acid continually 

 produced during the formation of the embryo, 

 but more particularly in the few weeks immedi- 

 ately preceding hatching. 



Many designers of hatching apparatus seem to 

 have had in view merely how to obtain the 

 greatest results on paper, the value of these 

 results does not appear to have received much 

 consideration. This or that apparatus will incu- 

 bate, and perhaps actually hatch so many thousand 

 eggs, and it requires little water and takes up next 

 to no space ! The important question, what is to be 

 done with the fry, never seems to have occurred 

 to the designer. Now the fact is that the fry 

 require nearly two square feet of surface per 

 thousand if they are afterwards to be fed in the 

 hatching troughs, and fully one square foot of 



