250 POULTRY CULTURE 



of development. As eggs are usually tested with an ordinary lamp, 

 anything noticeable in the shaded portion (as a dark spot, ring, or 

 lines) indicates a dead germ, and vacillation of the lower line of the 

 air space shows that decomposition is well advanced. By slightly 

 turning the egg as held large end up before the light, the condition 

 of the contents may be observed ; in the normally developing 

 fertile egg they appear solid, in the decaying egg, fluid. 



Period of incubation. The time required for incubation is for 

 fowls, 21 days ; pheasants, from 22 to 24 days ; turkeys, peafowl, and 

 guineas, 28 days ; ostriches, 42 days ; ducks, 28 days ; geese, from 

 30 to 35 days ; swans, 3 5 days, — these figures giving the average 

 periods for different types of each kind of poultry and for normal 

 development. It is noticeable that for the smaller kinds of poultry 

 the period of incubation is generally shorter. This is true also of 

 different types of .the same kind of poultry. The eggs of small, 

 active birds hatch sooner than those of the larger, more sluggish 

 ones. Broody birds of high temperature will (other things being 

 equal) hatch the same eggs sooner than will those of lower tempera- 

 ture. The young birds hatching long in advance of the normal 

 average time are likely to be precocious individuals. Those much 

 delayed are likely to lack vitality. As a rule, the best specimens 

 are those which hatch promptly after having taken the full period 

 for embryonic development, due allowance being made for differ- 

 ences in the type of the bird and in the birds incubating the eggs. 

 In fowls a hatch of Leghorns might be complete in twenty days ; 

 a hatch of Brahmas under the same conditions show not an egg 

 picked at that time. A difference of a day, or even two days, in 

 the apparent period of a hatch may occur, either through failure of 

 the incubating birds to sit closely on the eggs at the outset, or be- 

 cause of partial chilling of the eggs at a later stage of incubation. 

 In the first case the vitality of the young birds may not be at all 

 affected ; in the other they are likely to be weak. 



Chilling of eggs during incubation. The chilling of eggs cannot 

 be wholly avoided. A bird may become sick, or perhaps die on 

 the nest, before its condition is discovered ; and occasionally one, 

 though to all appearances in good health, quits sitting and stands up 

 in the nest. Such a case the novice may at first fail to distinguish 

 from the case of the bird that stands up occasionally (especially in 



