Figure 27. Baer's illustration from the first part of UBER 



ENTWICKLUNGSGESCHICHTE. 



1 . Transverse section of the embryo in the middle of the 

 first day. 



2. Transverse section of the embryo in the second half of 

 the first day. 



3. Transverse section of the embryo in the beginning of the 

 second day. 



4. Transverse section of the embryo at the end of the 

 second day. 



5 and 6. Transverse section of the embryos in the fourth day 

 (earliest and latest) . 



7. The same as in 6, longitudinal section. The designations 

 on all the figures of the transverse sections (1-6) : 

 a — spinal cord: b, b' — external border of the spinal 

 plate; c — upper border of it; be — spinal plate; 

 d — external, later lower border of the abdominal plate; 

 bd — abdominal plate: e — the bend of the serous layer; 

 de — skin part of the abdominal wall; f — border of the 

 lateral folds; g — lateral part of the amnion folds; deg — 

 amnion; h, i — upper and lower angles of the mesenteric plates; 

 k — vascular layer of the intestine; 1 — mucous layer of the 

 intestine; If — the false amnion of Wolff; m — Wolff's body; 

 o — aorta; p — urinary sac; n — opening the mesentery. 

 The designations on the figure of the longitudinal 

 section (7) : f — stomach; g — anterior entrance into 

 the digestive canal; gk — the unclosed part of the 

 intestine; e — respiratory apparatus; m — urinary sac; 

 p, p' — the band of the vascular, mucous, and serous 

 layers; q — the transfer of the embryo into the caudal 

 fold; pr — the head or cephalic fold; qs — caudal fold; 

 tu — the closed anterior and posterior fold of the 

 amnion; r, t, u f s — serous membrane, or the false 

 amnion of Pander; v — auricle; y — stem of the body vein. 



313 



