218 A. Willev, Foetal Membranes of the American Beaver (Oastor canadensis). 



27. Wilson, J. T. and J. P. Hill, Primitive Knot and Early 



Gastrulation Cavity co-existing with Independent Primitive Streak 

 in Ornithorhynchus, in: Proc. Roy. Soc. London, Vol. 71, 1903 

 p. 314—322. 



28. — , Observations on the Development of Ornithorhynchus, in: Phil. 



Trans. Roy. Soc. London (B) , Vol. 199, 1907, p. 31 — 168, 

 tab. 1—17. 



