3IO ORIGIN OF ALLANTOIS AND AMNION. 



of the organ. The main difficulty is the early development of the head-fold 

 of the amnion, since, from the position of the allantois, it might have been 

 anticipated that the tail-fold would be the first formed and most important 

 fold of the amnion. 



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(242) A. Gotte. Die Entw ickltmgsgesckichte d. Unke. Leipzig, 1875. 



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