230 BOARD OF AGRICULTURE. 



dense in the centre, and fading towards the periphery. Ev- 

 idently, the smaller whitish cells composing it, are more 

 crowded toward the centre than near the periphery ; they are 

 in larger number, and disposed in more numerous layers than 

 they are on the margin. On its lower edge it melts into the 

 other cells in such a way, that the point where it ceases and 

 the yolk begins, could hardly be marked. 



Now, that layer enlarges ; and as its circumference extends 

 it increases also in thickness, covering a larger surface of the 

 egg, and jienetrating to a greater depth within the yolk, but 

 still with indistinct limits. An increase in dimensions in 

 every direction is thus far the only change ; an additional 

 thickness toward the middle and an enlargement around the 

 margin. Next it alters slightly in form. Instead of being 

 circular, it is somewhat oblong, and one end is blunter than 

 the other. As this modification of the outline goes on, the 

 thickness becomes less uniform throughout. Two parallel 

 ridges arise upon the sides of the germ, at equal distance from 

 the middle line. This phase is generally represented as if a 

 longitudinal furrow were forming along the germ. It is a 

 furrow, if you will, but it is the result of the depression en- 

 closed between the walls formed by these parallel ridges. 

 All this goes on by an impulse, of the nature or cause of which 

 we have no conception. It is easy to watch the growth of an 

 egg so as to bring this process, in its successive phases, before 

 the eye. You need only place your eggs in a breeding-ma- 

 chine, marking the hour at which you put in each egg. You 

 may thus know exactly how old the germ is, how long the 

 transformations have been going on, and as the chronology of 

 this growth is well ascertained, being familiar to embry- 

 ologists, you can take out of your machine an egg at any 

 stage and examine its condition, knowing beforehand, from 

 the record made of all these facts, in what period of develop- 

 ment you will find the germ. 



As these ridges rise in height, they do not remain just 

 parallel, but diverge, as it were, on one side, and so diverg- 

 ing the layer itself widens on that same side. This diver- 

 gence gradually increases, and as it increases, instead of 

 being a mere curve, it begins to be undulating. Now, this 

 germ has already two ends distinctly differentiated, while 



