36 



CHAPTER IV. 



EGGS AND INCUBATTON. " 



The motto " omue animal ex ovo" adopted by the New York State Poultry Society, aptly 

 expresses a tmth well known to all physiologists. All real animal life is developed from the egg- 

 form ; the only difference consisting in the mode of development, which in some cases is entirely 

 completed within the body of the female, whilst in others more or less of the process is carried 

 on after separation from her. It is in these latter cases that some kind of hard case or shell 

 becomes obviously necessary for the protection of the egg until the embryo is ready to commence 

 its active existence ; and as in the case of birds vvc find the whole egg-structure in the most 

 perfectly organised form, it may be proper to give a very short and popular description of 

 its formation. 



i-ig. 10. 



The ovary of a hen during or near her laying season presents an appearance much like that 

 of a cluster of fruit, and is very accurately shown by the illustration (Fig. 1 6). There are more- 

 propcrly two such organs in every bird ; but one remains merely rudimentary and undeveloped, 

 the fertile cue being almost always that on the left of the spine, to which it is attached 

 by means of the peritoneal membrane. By the ovary the essential part of the egg, which con- 

 sists of the germ, and also the yolk, are formed, each egg being contained within a thin and 

 transparent ovisac, connected by a narrow stem or pedicle with the ovarj'. These rudimentary 



