210 GENERATION. 



Where the allantois covers the chick it adheres to the amnios, making 

 but one thin membrane between them, bnt it never becomes attached 

 to the membrana lutei or vitelli 1 . As it extends, it would appear to 

 push from the chick the remaining slime towards the opposite side to 

 that of the chick, as it were clearing the yolk of it more and more, so 

 that the slime becomes smaller, and at last lies like an oblong body 

 close and adhering to the cicatrix of the yolk. So far as these mem- 

 branes are attached to the membranes of the yolk, they would appear 

 to detach themselves from it by the time it is ready to be absorbed into 

 the cavity of the abdomen ; for none of the other membranes are taken 

 in with it, and it has no other attachment to the abdomen in any of 

 this class of animals. 



Of the Use of those Membranes as they arise. 



The formation of the chick seems to be but little prior to the forma- 

 tion of the membrana vitelli [germinal membrane], if at all prior ; for 

 among the first appearances is a spreading of the cicatricula, and the 

 centre would appear to contain a fluid. That the formation of the chick is 

 considerably prior to the formation of the other membranes is evident ; 

 therefore it might be asked, how the chick is nourished, and other 

 functions carried on, till those other membranes are formed ? supposing 

 that they absorb the slime. But the membrana lutei [germinal mem- 

 brane] performs this office, at least at this time, and there was a certain 

 space of the membrana vitelli [germinal membrane] that had the powers 

 of forming vessels and red blood, and which became very vascular. This 

 membrane would appear to answer two purposes, one for the purpose of 

 the chick, another as a covering to conduct the whole yolk into the 

 abdomen. 



That the membrane which I have called allantois, from its containing 

 lu-ine, answers other important purposes, must appear evident from its 

 extent being far beyond what would answer that purpose. I conceive 

 that the side of this bag, which surrounds and is in contact with the 

 albumen, acts as the chorion or placenta, for it must be by this surface 

 that the albumen is absorbed, and the chick supported. The external 

 part of this bag, which comes in contact with the shell, and as it 

 enlarges lines more and more of it, till at last it lines it everywhere, I 

 conceive to be the lungs, for it is the only part that comes in contact 

 with the air ; and on opening an egg pretty far gone, I find that the 

 blood in the veins is scarlet, while it is of the modena colour in the 



1 ["Vitellicle, or vitelline portion of the germinal membrane.] 



