i'ATHOLOOIC OVA, ALBINO RAT 



133 



•ct pi. - 



1-V e ' BCI ■ 



Fig. S Egg-cylinder of albino rat showing retarded development of ecto- 

 dermal node and of the formation of the antimesometrial portion of the pro- 

 amniotic cavity. X 200. Rat No. 94, S days after the beginning of insemina- 

 tion. ect.pl., ectoplacental cone or Trager; v.ent., visceral entoderm; met.pr., 

 mesometrial portion of the proamniotic cavity; p.ect., parietal or transitory 

 ectoderm; pr.emb.ent., primary embryonic entoderm; ect.n., ectodermal node; 

 a.met.pr., imperfectly developed antimesometrial portion of proamniotic cavity; 

 ex.ect., extraembryonic ectoderm. 



ectoderm, in structure and relation to decidual crypt, are to be 

 regarded as of normal development. The visceral entoderm, 

 surrounding the extraembryonic ectodermal portion of the egg- 

 cylinder, is of normal structure, showing the three zones evidenc- 



