MAMMALIA. 



183 



hypoblastic mesoblast already described in the chick (p. 128 and 129). 

 The stage just described has only been met with by Van Beneden 1 . 



A diagrammatic view of the whole blastodermic vesicle at about 

 the beginning of the seventh day is given in fig. 137. The em- 

 bryonic area is represented in white. The line r/e in B shews the 



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1 Kolliker does not believe in the existence of this stage, having never met with it 

 himself. It appears to me, however, more probable that Kolliker has failed to obtain 

 it, than that Van Beneden has been guilty of such an extraordinary blunder as to have 



rli'M>nl>r 1 ;i st;i!_'p which has no existence. 



