of the vascular area around the embryo, or more 

 exactly around the amnion covering it, a vesicle 

 must be formed .... 



Wolff noticed that this vesicle can be seen distinctly, 

 although it is not expressed identically in all eggs, and 

 he considered that the other investigators did not notice it, 

 because, in the first stages of incubation, they never 

 examined the lower surface of the embryo lying on the yolk. 

 In addition, he did not see this formation himself up to 

 1764, although he had investigated the developing eggs 

 during the five previous years. 



"All," Wolff continued, "who did not see the true amnion 

 during its first appearance, or at least in the third or 

 fourth day of incubation, assumed that this vesicle is the 

 amnion, because the described vesicle is swollen and distended 

 with fluid. It seems directly adjacent to the embryo, while 

 the amnion itself, due to its extreme thinness and trans- 

 parency, may remain unnoticed. Therefore, I called this 

 formation the false amnion, although it does not properly 

 possess any similarity with the true amnion. "4 



It is not easy to translate into the language of recent 

 embryology his description. Here, apparently, the descriptions 

 of different formations are combined: on one hand Wolff 

 dealt with the trunk folds, the apex of which was submerged 

 inside the embryo. Finally this apex separates from the yolk 

 sac. On the other hand, he saw a deepening of the endoderm, 

 submerged from below in the embryo. All of this composed a 

 picture of what Wolff described as the false amnion. 5 



Cited places in § 36 and 37 under title "Vesicle, 

 appearing in the lower surface of the transparent zone, 

 or false amnion" (pp. 434 - 437) . 



Nearly the same, K. M. Baer evaluated the idea of the 

 Wolffian term as "false amnion," when he cited the work of 

 Wolff in his classical work, HISTORY OF ANIMAL 

 DEVELOPMENT (UBER ENTWICKELUNGSGESCHICHTE DER 

 THIERE. BEOBACHTUNG UND REFLEXION, v. I, part I, 5 c) 



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