Fig. 



20. 



Fig. 



21. 



Fig. 



22. 



Fig. 



23. 



Fig. 



24. 



PLATE II 

 LATER EMBRYOS OF HETERODOHTUS JAPOHiCUS 



A cleared embryo with 18 complete somites. Measured on the slide, it is 3.5 mm. (about one-eighth 

 inch) long. 



Surface view of an embryo with about 24 somites. 



Like some of the embryos represented in the surface views that follow, this one appears to have been drawn at a lower 

 magnification than that used for cleared preparations. 



Surface view of an embryo with about 25 somites. 

 A cleared embryo with at least 26 somites. 

 Surface view of an embryo with at least 28 somites. 



This figure was drawn from the left side, but it has been reversed to facilitate comparison with other figures on this plate. 



Fig. 25. Surface view of an embryo with about 35 somites. This figure, like the preceding, was drawn from 

 the left side but has been reversed. 



Fig. 26. A cleared embryo with about 37 complete somites. 



Fig. 27. An embryo with about 41 complete somites, drawn after being cleared. 



Fig. 28. Surface view of an embryo with at least 50 complete somites. 



Fig. 29. An embryo with about 55 complete somites, drawn in surface view. 



Fig. 30. Head and anterior part of the body of a cleared embryo. The number of somites is unknown. 



Fig. 31. Surface view of an embryo with about 74 somites, now represented by myomeres. 



Fig. 32. An embryo with about 85 myomeres, drawn in surface view. 



Since all the figures of this plate are lateral views, the number of somites (in later stages represented by myomeres) is 

 recorded for one side only. 



