YOUTH AND MATURITY. 



Incubation. — Having completed the task of laying her eggs, 

 the female bird enters upon the process of incubation or hatching, 

 in which she is often relieved by the male. The process is accel- 

 erated by the warmth of the body of the female, which now pos- 

 sesses a high temperature. Some birds utilize the heat of the sun 

 and of vegetable fermentation. The duration of the hatching pro- 

 cess varies with different kinds of birds. The Ostrich takes from 

 fifty-five to sixty days ; the Humming-bird only ten or twelve, and 

 birds, on an average, from sixteen to twenty-five days. For the 

 formation and development of the chick or young bird, a temper- 

 ature of about ninety-six degrees (Fahrenheit) is required. The 

 requisite warmth may be obtained from the parent bird, or by arti- 

 ficial means, as breeding-ovens, etc. That famous story-teller, 

 Pliny, relates that Julia Augusta, the wife of Tiberius, hatched 

 eggs in her bosom. Besides warmth, the access of atmospheric 

 ; ir is absolutely necessary to the development of the chick. With- 

 out this, the egg will inevitably become addled. 



Progress of Development. — The effect of warmth may be 

 seen after a few hours, and in hen's eggs, in about ten or twelve 

 hours after the commencement of the incubation. The w T hite round 

 dot, or treddle, assumes a more oblong form, and its surrounding 

 white rings are widened and increased in number. At the begin- 

 ning of the second day, a small projection appears, and, in thirty 

 hours, there is seen in its bladder-like cavity filled with a clear 

 liquid, a turbid, cloudy jelly. Toward the end of the second day, 

 the first traces of blood appear in reddish dots, streaks, and lines, 

 gradually combining and forming a sort of net-work. These are 

 the rudiments of the blood-vessels, which appear more distinct on 

 the third day, forming branches at first, and finally a central point, 

 eventually developing into the heart. Soon after its first manifes- 

 tation, it begins to move ; it expands and contracts : life has awak- 

 ened, and manifests itself. Next are observed three dots like small 

 bubbles, which originate the head, two of them being rudimental 

 eyes. These are of a dark hue, the other dot is colorless. Now 

 appears a row of little bubbles in pairs, which, taking a downward 

 course, will combine into a backbone. Two developing plates 

 mark out the circuit of the abdomen, and, at the same time, are 

 exhibited traces of the stomach and the intestines. 



On the fourth day, the yelk is enlarged, but loosened and thin- 

 ned ; the albumen is decreased, and the blood-vessels increased ; 

 the separation of arteries from veins is progressing ; the head is bent 

 down toward the posterior portion ; the heart becomes more dis- 

 tinct in its manifestations ; the vessels of the brain, and the rudi- 

 ments of the mandibles, the wings, the legs, and the liver begin to 

 be discerned, the last as a reddish gray jelly-like mass. 



The fifth day presents the heart and intestines more fully devel- 

 oped, and the breast almost covered by a compound substance, 

 beginning from the backbone and the wings. At the close of this 

 day, the beginning of the lungs is observable ; the heart is sur- 

 rounded by a transparent sack, and the backbone is plainly shown. 

 On the sixth day, the egg-skin is formed, appearing like two 

 closed bladders — the external one for the cutis and the internal for 

 the amnion. On the abdomen, enlarged by the admixture of al- 

 bumen, the vessels are spread out ; the several parts of the em- 

 bryo are more distinctly developed, and it sometimes exhibits, at 

 the close of this day, a kind of motion. 



The embryo, on the seventh day, swims in the amniotic fluid ; 

 it is now about an inch long, and its head is almost as large as its 

 body. The brain, appearing like a soft, slimy mass, presents to 

 view its different parts, and the backbone shows traces of the be- 

 ginnings of cartilaginous formations. The ribs are seen in white 

 streaks. The throat, the crop, the gizzard, gall-bladder, and milt 

 are likewise discernible. 



The eighth day exhibits the chick increased in size ; the breast- 

 bone begins to be formed, and white streaks, the beginnings of 

 muscles, appear around the developing bones. 



The ninth day discloses a small process on the head, forming the 



upper mandible ; the transparent eyelids become visible around the 

 eyes ; the heart, inclosed in its sack, pulsates twelve times in a min- 

 ute ; the brain becomes more compact, and its cartilaginous bony 

 portions assume greater distinctness. 



On the tenth and eleventh days, the embryo still increases in 

 size ; the large head is considerably lessened, and lies between the 

 legs, almost covered by the wings ; the gall-bladder is filled, and 

 on the skin are seen small protuberances, whence feathers will 

 spring in due time. On the two following days, the chick begins 

 to move visibly, and attains a - length of about two inches ; downy 

 feathers appear on the part of the body near the pelvis, and on the 

 back, wings, and legs ; the limbs are more fully developed, and the 

 feet and toes begin to be covered with white scales ; the bill pre- 

 sents itself in a cartilaginous form ; the brain has almost attained 

 its future size and shape ; the cartilaginous brain cover (the skull) 

 begins to ossify, and the lungs gain their proportionate size ; the 

 cartilaginous rings are traceable on the windpipe, and the urinary 

 vessels in the kidneys, while the urinary tube, the ovaries, and the 

 ovi-director are easily distinguished. The muscles are soft and of 

 a white color, the large sinews are more distinct, and the cartilag- 

 inous forms of the bones begin to ossify. 



On the fifteenth and sixteenth days, the chick reaches almost its 

 full size ; the white scales on the feet and toes are converted into a 

 horny casing ; the larger wing-feathers begin to shoot out, and the 

 embryo chick, if disturbed, opens and shuts its beak. During the 

 seventeenth, eighteenth, and nineteenth days, the cutis is spread 

 over the whole inner surface of the egg ; the albumen becomes al- 

 most totally absent ; and the yelk-bag collapses and passes through 

 the navel ring into the abdominal cavity. The chick dons its 

 feathery robe, lying inclosed in the amnio, folded in a compact 

 form, and leaning sideways on its breast, with its head under the 

 right wing, and its legs drawn up to the abdomen. It begins to 

 be active now ; it opens and shuts its bill, gasps for 'breath, and often 

 utters a distinct "peep." The head is completely developed, and 

 the brain has assumed its permanent form. 



On the last two days, the yelk altogether disappears in the cav- 

 ity of the abdomen, and the chick fills the entire egg. It breathes, 

 peeps, and, if taken out of the egg, puts out its tongue. Several 

 hours before its exit, the chick, on the twenty-first day, rubs the 

 horny protuberance upon its bill against the shell of the egg. This 

 begins to crack, little pieces fall off, the skin of the shell is torn 

 asunder, and the chick, stretching out its new-found legs, pulls its 

 head from under its wing, and comes forth from its prison-house 

 to air, light, and freedom. 



Youth and Maturity. 



Growth. — A few birds only are as fully developed in the egg 

 as chickens and ducks, and those only that are destined by nature 

 to follow their parents and run about as soon as they make their 

 debut in the world. The birds that have, when full grown, the 

 greatest motility and power, are among the most helpless in in- 

 fancy. Those that run from the nest (Nest-runners), come into the 

 world feathered and with developed senses, and have a pleasing 

 appearance, being already, to a certain extent, perfected. Others 

 that attain similar perfection by slow degrees, and remain, in the 

 meantime, in the nest (Nest-squatters), are ungraceful, and even de- 

 formed in appearance ; their development requiring a longer or 

 shorter time, according to their kind. The smaller kinds of nest- 

 squatters are usually fledged in about three weeks ; the larger often 

 require several months. Most of them take years to become equal 

 to their parents, for the youth of a bird can only be said to be ended 

 when it appears in the dress of its parents. Manj>» of these birds 

 have at first a feathery dress, which has no resemblance to that of 

 the parents. A majority of these young birds are covered like the 

 females, and the difference of sex can be known by the external 

 appearance only when they have assumed the dress of maturity. 



