PLATE I 



Pygoscelis papua. 



Fig. I. Embryo, stage 9 (No. i). ap, area pellucida; av, area vasculosa; 

 fg, fore-gut ; mf, medullary fold ; ntc, notochord ; ps, primitive streak. 



Fig. 2. Embryo, stage 13 (No. 2). ao, aorta; Ze, left eye; ms, mesoderm 

 segment ; nt, neural tube ; ot, otocyst ; re, right eye ; va, vitelline artery ; 

 ■vv, vitelline vein. 



