OUTLINES OF THE DEVELOPMENT OF THE TUATAEA. 87 



Figs. 96—100. Stage O. 



Pig. 96,— Embryo 103, seen from below, with the foetal membranes intact, 

 as an opaque object in spirit. X 5. 



Tig. 97. — Embryo 92, seen from below as an opaque object in spirit, show- 

 ing the front end partially withdrawn from the invaginated yolk-sac. X 5. 



ElG. 98.— Embryo 92, from the left side, after removal of the foetal mem- 

 braues, seen as an opaque object in spirit. X 5. 



EiG. 99.— Embryo 92. Ventral view of head, seen as an opaque object in 

 spirit. X 10. 



EiG. 100.— Embryo 92. Sketch of living embryo from above, to show 

 allantois, allantoic and vitelline circulations. (The arrows show the direction 

 ill which the blood was flowing ; only the veins were conspicuous : the 

 transparent serous envelope is not indicated.) X 5. 



EiG. 101. Stage P. 

 Pig. 101.— Embryo 87, drawn from above (right side of embryo) as an 

 opaque object in spirit, to show the complete extrication of the front part of 

 the embryo from the yolk-sac. The amnion and serous envelope have been 

 partially removed, and the allantois has shrivelled, x 5. 



Pigs. 102, 103. Stage Q. 

 Pig. 102. — Embryo 1, drawn from the right side as an opaque object in 

 spirit, after removal of the foetal membranes. X 5. 



Pig. 103. — Embryo 1, drawn as before, but from the left side, X 5, 



Pigs. 104—107. Stage R. 



Pig. 104. — Embryo 2, drawn from the right side as an opaque object in 

 spirit, after removal of the foetal membranes. X 5. 



Pig. 105. — Embryo 2, drawn from above, as before. X 5. 



Pig. 106. — Embryo 3. Portion of yolk-sac, with yolk particles adhering to 

 the absorbent vessels so as to give rise to a radially columnar structure ; seen 

 as an opaque object in spirit on a dark background. X 5. 



Pig, 107. — Embryo 3. Yolk-spheres and crystalloids ; drawn from a pre- 

 paration mounted in glycerine, after treatment with Kleinenberg's picric acid 

 and alcohol. Zeiss D, ocular 3. 



