Figure 24. "Ideal cross-section" by Pander 



1 — XX — a passage of the yolk membrane in the chalazae, in 

 the nucleus of the cover; "blastoderm of non- 

 incubated ... (a gap in Pander's text) ; 



2 — blastoderm of the second day, composed of three layers; 



CO — the mucous layer; dd. — vascular layer; co — serous 

 layer, f — fetus; 



3 — here the layer of the blastoderm is drawn so as to show 



the change of the serous layer, which at gg has formed 

 the primary folds ; 



4 — schematic presentation of the vessels of the layers of 



the blastoderm. The serous layer forms a fold on the 

 tail at n and a fold on the head at m , and then 

 together with other membranes it spreads in order to 

 cover the yolk, which they cover more and more. The 

 umbilical ring (Ik) here is still very wide. Parts 

 of the serous membrane I and {, form the amnion, 

 which will later extend through the back of the 

 embryo and close by means of the adhesion of the 

 borders of the folds (77) . The vascular layer, 

 following behind the serous layer, at f forms the 

 heart and the large arteries which are its continuation, 

 and at g (Pander is not sure about this) the sac of 

 the chorion or the allantois. The mucous layer at 

 f forms the food canal, and at g the colon, and 

 between g and f it forms the middle intestine of 

 Wolff (78) ; 



5 — A — longitudinal section, c, d, e. designating the same as 

 before; hh — level of the transverse section presented 

 in 5B; v — area in which the heart and food canal 

 develop; w — place of formation of the colon and 

 apparently the chorion; z — spinal cord; G — view from 

 below (from the side of the yolk) the embryo of 5A; 

 aact — area between kk in Fig. A (i.e. the umbilicus) ; 

 bbh — the head portion (gk in Fig. A) ; q- — the tail 

 portion (fk in Fig. A) ; dd — the translucent spinal 

 cord with the primary folds; 



6 — A and B — the same as Fig. 5A and 5B; at Ctb the vascular 

 membrane has formed the heart C/ ) ; 2 — spinal cord; 

 X — head depression of the yolk; 



268 



