PIG 



RABBIT 



MONKEY 



MAK 



A 



FIG. 23. EMBRYOS OF THE PIG, RABBIT, MONKEY, AND MAN 

 Comparison at corresponding stages of development. The embryos of each 

 animal are arranged in the vertical columns according to age, beginning 

 with the youngest stage at the top. Stage A of the human embryo is 

 full}* labelled, and the corresponding structures in the other embryos can 

 be noted. 



a, head region; b, eye; c, ear; d, gill slits; e, heart; f, fore limb; g, 

 primitive muscle segments: h, hind limb; i, tail region. 



Slightly modified from K. (nienther, after Keibel. 



