176 Ornithology. 



great, her feelings would dictate the necessity of leaving them for 

 a time to cool. At the early period of incubation birds quit their 

 eggs more frequently than at the time the foetus is more perfect. 

 Yet, in the advanced state, the embryo yOung is not in more! 

 danger of being destroyed, if so much ; for a living foetus is fre- 

 quently found that has been taken from the nest two days- If,, 

 however, the young is within a few hours excluded, and the egg 

 is suffered to be sometime cold, it either dies, or becomes so 

 weak, as not to be able to extricate itself from the shell. Vari- 

 ous degrees of heat will enlarge the embryo young, but regular 

 heat ceems necessary to its production; and yet artificial heat, 

 regulated by the brooding of a bird, will not produce young with 

 certainty. In Egypt, a vast quantity of eggs are hatched by ar- 

 tificial heat in stoves. It is probable, however, one third or one 

 fourth miscarry. 



The male birds of some species supply the place ofthe females 

 on the nest; but then it is of short duration, and rarely, if ever, 

 when eggs are near hatching: at that time the female is frequently 

 fed by the male. This is not common to all species, but very 

 conspicuous in the rook, the pigeon and many others. Many 

 species of birds possess a reservoir for food, called a craw^ or 

 crop; this seems to answer the same purpose as the first stomach 

 in ruminating animals. Here it is the food is softened and pre- 

 pared for the stomach; from this reservoir it is by some ejected 

 for the purpose of feeding their yoimg; conspicuous in the pigeon. 



The rook has a small pouch under the tongue, in which it car- 

 ries food to its young. It is probable the use of the craw may 

 be extended further than is generally imagined; for, besides the 

 common preparation of the food to assist its digestion in the 

 stomach, there are some species tha.t actually secrete a lacteal 

 substance in the breeding season, which, mixing with the half- 

 digested food, is ejected to feed and nourish the young. The 

 mammce, from which this milky liquor is produced, are situated 

 on each side ofthe upper part of the breast immediately under the 

 craw. In the female turtle dove, these glands are tumid, with 

 milky secretions, and we believe it common to both sexes of the 

 dove genus. The comorant or pehcan genus possess no craw; 

 but to supply its place, they have a loose skin at the base of the 

 under mandibles, capable of great distention, in which they carry 

 fish to their young. 



We shall conclude this article by giving an account of Malpighi 

 and Haller's experiments on the hatching of a hen's egg. 



Previous to putting the eggs to the hen, they first examined the 

 cicatricula, which they considerde as the most important part of 



