226 BOARD OF AGRICULTURE. 



steadily until they reach certain dimensions. This growth 

 consists mainly in the enlargement of the yolk, which is the 

 essential part of the egg ; in fact, the yolk is the living por- 

 tion of the egg. It is that which from the beginning, is 

 increasing ; it is that in w^hich all the changes take place pre- 

 paratory to the formation of the germ ; it is through the yolk 

 that the substance of the young is made ; it is in the yolk and 

 with the yolk that the growth begins, and it is through the 

 transformation of the yolk that the body of the new being is 

 brought into its peculiar condition as a germ, and finally ac- 

 quires the character of a new being like its parent. 



One point in which eggs diflier most is their size. In the 

 highest animals, in all the mammalia, that is in all warm- 

 blooded animals bringing forth living young, the eggs are 

 exceedingly small, so small as hardly to be visible to the 

 naked eye. Only a well-trained eye can perceive the egg of 

 a ral)bit or the egg of a dog, at the time it has completed its 

 growth prior to the formation of the germ. Examine the 

 egg then, and yon can still hardly distinguish it, even after 

 a good deal of practice, from the egg of the hen or of any 

 other bird, at the same stage, or from that of a reptile, turtle, 

 serpent or frog, or from that of any fish, or indeed from that 

 of any other animal, be it the crab, the lobster, the oyster, 

 the polyp, the jelly-fish, no matter what, in the whole animal 

 kingdom. You will find that at a certain time the eggs of 

 all of them have identically the same structure. Now, these 

 eggs grow to certain dimensions, and during that growth, 

 undergo changes which prepare the formation of the germ. 

 What are those changes? They are vital processes within 

 the yolk ; changes in its substance going on under no exter- 

 nal influences except the raised temperature to which some 

 eggs are submitted during incubation, or during gestation. 

 It is a marvellous process, that of this inner life of the 

 yolk, leading to a result so extraordinary as the formation 

 of a new living being. Physiology, as we learn it in our 

 books, made up as it has been from the study of adult 

 animals, gives us no idea of such a mode of growth. We 

 are accnstomed to see an animal growing when it is fed. It 

 takes in food ; that food is digested in particular organs ; 

 there is a stomach, an alimentary canal, through which the 



