ABSTRACT
In 1971 A. G. Hendrickx13 and his colleagues published the Embryology of the Baboon which described the external and internal features of 23 stages of baboon development from the fertilized ovum to the end of the embryonic stage. The criteria used for classification of the baboon embryos was almost identical to those used by Streeter6-10 for human embryos. Comparison of stages 1 to 8 of human and baboon embryos is rendered difficult by their different mode of implantation and placentation and, as with the human embryos, these early stages will merely be listed (Table 4). Carnegie Stages 1 to 8 of Baboon Embryos
Carnegie stage
Age (days)
Features
1
1
Fertilization
2
2—5
From 4 to 63 cells
3
5—8
Free blastocyst
4
9±1
Implanting blastocyst
5
10±1
Implanted blastocyst
6
11—15
Primitive chorionic villi, bilaminar embryonic disc
7
16—18
Branching chorionic villi, primitive streak
8
17—19
Primitive groove, beginning notochordal canal in older embryos
