PLATE XX & Continued. 
Fig. 10. — Section through an ovum, slightly younger than fig. 1. 
Showing the primitive cumulus and the columnar character of the cells 
of one half of the blastoderm. 
Fig. 11. — Section through an embryo of the same age as fig. 2. 
Showing the median thickening of the blastoderm. 
Fig. 12. — Transverse section through the ventral plate of a somewhat 
older embryo. Showing the division of the ventral plate into epiblast and 
mesoblast. 
Fig. 13. — Section through the ventral plate of an embryo of the same 
age as fig. 3, showing the division of the mesoblast of the ventral plate 
into two mesoblastic bands. 
Fig. 14. — Transverse section through an embryo of the same age as 
fig. 5, passing through an abdominal segment above and a thoracic 
segment below. 
Fig. 15 — Longitudinal section slightly to one side of the middle line 
through an embryo of the same age. 
Fig. 16. — Tranverse section through the ventral plate in the thoracic 
region of an embryo of the same age as fig. 7. 
Fig. 17. — Transverse section through the procephalic lobes of an 
embryo of the same age. gr. Section of hemicircular groove in pro- 
cephalic lobe. 
Fig. 18. — Transverse section through the thoracic region of an 
embryo of the same age as fig. 8. 
Fig. 19. — Section through the procephalic lobes of an embryo of the 
same age. ^ 
Fig. 20 a, 6, c, d, e . — Five sections through an embryo of the same 
age as fig. 9. a and b are sections through the procephalic lobes, 
c through the front part of the thorax, d cuts transversely the 
posterior parts of the thorax, and longitudinally and horizontally the 
ventral surface of the abdomen, e cuts the posterior part of the ab- 
domen longitudinally and horizontally, and shows the commencement 
of the mesenteron. 
Fig. 21. — Longitudinal and vertical section of an embryo of the same 
age. The section passes somewhat to one side of the middle line, and 
shows the structure of the nervous system. 
Fig. 22. — Transverse section through the dorsal part of the abdomen 
of an embryo of the same stage as fig. 9. 
