142 THE HISTOKY OF ANIMALS. [B. VI* 



a kiss, but afterwards lie mounts without kissing, but 

 younger birds always kiss before copulation. This also is 

 peculiar to these birds. The females kiss and mount upoii 

 each other like the males, when there is no male present. 

 They do not project anything into each other, but produce 

 more eggs than those which produce fertile ones ; from these 

 eggs nothing is hatched, but they are all barren. 





 CHAPTER III. 



1. THE production of the bird from the egg is alike in then: 

 all, but the period of completion varies, as I observed be- 

 fore. In domestic fowls the first sign of alteration takes 

 place after three days and nights. This period is longer in 

 larger birds, and shorter in small birds. During this period 

 the upper part of the yolk advances to the small extremity 

 of the egg, which is the beginning of the egg. This is the 

 part from which the chicken is excluded, and the heart is 

 visible like a red spot in the white of the egg. 



2. This spot palpitates and moves as though it were en- 

 dued with life. From this, as it increases, two involved 

 sanguineous passages like veins lead to each of the sur- 

 rounding tunics ; and a membrane which has sanguineous 

 passages encloses the white at this period, and separates it 

 from the venous passages. A short time afterwards the 

 body is distinguished, at first very small and white, but the 

 head is distinct, and in this the eyes are the most enlarged. 

 And this continues for some time, for afterwards the eyes are 

 reduced in size and approach each other, but the lower part 

 of the body has not at first any proportion to the upper part. 



3. One of the passages from the heart extends into a 

 circle around the embryo, and the other to the yolk, as if 

 it were an umbilical cord. The origin of the young bird 

 is in the white, its nutriment is derived from the yolk 

 through the umbilical cord. On the tenth day, the whole 

 of the young bird and all its parts are distinct, but its 

 head is still larger than the rest of the body, and the eyes 

 are larger than the rest of the head. They have no sense 

 of sight. If the eyes are taken out at this period, they 

 are larger than beans, and black ; when the skin is 

 taken from them, they are seen to contain a white and coJd 



