108 HABITS OF BIRDS. 



contributing to its enlarged growth. By cutting 

 through both these envelopes with great care, we 

 bring into view a third, of extreme delicacy, very 

 transparent, and of a white colour. This seems to be 

 unconnected with the two envelopes, and no blood- 

 vessels are seen branching through its substance. 

 Immediately within this transparent envelope, which 

 is similar in texture to our own scarf-skin (epidermis) 

 lies the yolk, as yet imperfectly formed ; and at the 

 side opposite to that where it was attached to the 

 egg-organ, is placed the rudiment of the future chick 

 (cicatricula). The latter consists of a white bland 

 substance which is not separated by any membrane 

 from the yellow matter of the yolk, but merely lies 

 over it, waiting till the heat imparted in the process 

 of hatching shall develope it so that it may feed upon 

 the yolk supplied for its first nourishment. 



This germ, or rudiment of the chick, has no con- 

 nection, M. Dutrochet assures us, with the proper 

 enveloping membrane of the yolk, a fact which he 

 took great pains to ascertain. He removed the proper 

 membrane of the yolk, which did not exhibit the 

 slightest adhesion to the germ, but left it perfectly 

 entire; and when he examined the membrane thus re- 

 moved by means of the microscope, he could not 

 perceive the least breach in its substance, nor any 

 difference in its texture or structure. At the point 

 opposite to this, there may be observed, as the egg 

 enlarges, a whitish line or strealc, occupying nearly a 

 third of the sphere, which indicates the approaching 

 rupture through which the egg is about to escape 

 from the pouch where it has been confined. In fact, 

 when the egg is separated, the pouch, formed by the 

 two enveloping membranes already mentioned, opens 

 in the direction of this whitish line, and the egg co- 

 vered by its outer membrane (which is not connecte " 





