Hens and chickens.—Chickens which have been hatched in the natural manner are, from the first, under the control of the hen (Fig. 194), and her anxious care for their welfare has always been considered one of the most beautiful examples of the maternal instinct. In their defence her courage is unbounded; should she discover a succulent worm or other dainty morsel, her ordinary complacent cluck changes to a note of invitation, to which the brood at once responds; and at her danger-signal the chickens run to take refuge under her wings, or crouch motionless against the ground. The chirp of a chick also is capable of expressing several states of feeling, such as contentment, pleasure, alarm, and distress. These different notes are not only perfectly intelligible to the hen, but are familiar to anyone who has had experience of poultry. Fig. 194.—Hen and Chickens. In the face of these well-known instances of the perfect understanding between the hen and her chickens, it is somewhat surprising to find that chickens, hatched apart from the hen and then placed with the rest of the brood after a few days, at first pay very little attention to the hen, except for their instinctive tendency to nestle into warm places, and do not seem to understand her clucks. [Pg 299] Adult fowls.—The down-feathers are soon shed and replaced by the true plumage, and the chicken gradually takes on the appearance of the adult. A marked difference is generally to be seen between the cocks and hens (Fig. 195) of any breed of poultry. The cock is usually provided with flowing tail-feathers, hackles (elongated feathers on the neck and loins), a prominent comb, and “spurs”—features which are either absent or much less perfectly developed in the hens. As great differences exist between the voices of the two sexes, the crow by which the pugnacious male challenges his rivals, and the cackle of the hen when she has laid an egg, being familiar examples. Fig. 195.—Cock and Hens. [Pg 300] EXERCISES ON CHAPTER XVI. 1. Point out the differences in appearance and position between the white and yolk of a fowl’s egg. What becomes of each during the development of the egg? 2. When does the heart of a chick begin to beat? Describe its appearance at this time, and explain what must be done to expose it to view. 3. Explain exactly where the chick is to be found in a fertile egg which has been incubated for three days. How big is a chick of that age? Of what colour is it? Does it give any signs of life? (1898) 4. What is the amnion? Where, in a developing chick, is it to be found, what is its appearance, when and how is it formed, and what is its use? 5. Explain the nature and use of the “balancers” of an egg. 6. Explain how a developing chick breathes.