MAMMALIA. 



183 



hypoblastic mesoblast alread}'- described in the chick (p. 128 and 129). 

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



A diaoframmatic view of the whole blastodermic vesicle at about 

 the beginning of the seventh day is given m lig. 137. The em- 

 bryonic area is represented in white. The line ge in B shews the 



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^ KoUiker does not believe in the existence of this stage, having never met with it 

 himself. It apjiears to me, however, more probable that KSlliker has failed to obtain 

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

 described a stage which has no existence. 



