AMBL7ST0MA PUNGTATUM. 19 



Figure 8 — Continued. 



most prominent features, in. f. c. cephalic portion of 

 medullary folds; m. p. medullary plate; m. g. medul- 

 lary groove. 



Figure 9. — A ventral view, le?s magnified, of a more advanced sta?e. 

 c, the cephalic end of the medullary tube ; a, the anal 

 end of same. 



Figure 10. — Lateral view of same specimen from which figures 1 and 

 8 were taken. Figure 10 was made twelve hours after 

 figure 8. n. c. neural canal ; e, optic vesicle; t, throat 

 region ; a, anus. 



Figure 11. — Dorso-lateral view of same specimen as figure 10. m.f. I. 

 line of union of medullary folds; m.f. a. anal portion 

 of medullary folds. Other letters as before. 



Figure 12. — Ventral view of specimen from which figures 10 and 11 

 were made, cl, the swollen mass from which the cau- 

 dal portion is mainly developed. Other letters as 

 before. 



Figure 13. — Lateral view at a later stage, e, optic vesicle; mb, mid- 

 brain ; bn, the lobe from which the liranchiae are to 

 be developed ; bo, lobe from which the anterior limb 

 develops ; jjr, the external indications of the proto- 

 vertebrae ; /, throat region. From the condition rep- 

 resented in Figure 12 to that of Figure 13 the change 

 of outline, with the exception of the increased cranial 

 flexure, has been slight. The energy has been used in 

 developing special parts, rather than in general growth. 



Figure 14. — A. ventral view. The embryo has been growing rapidly 

 in the last two or three days ; is much elongated, and 

 the different regions of the body are acquiring definite 

 limits. Letters as in Figure 13. Unfortunately, there 

 is no reference to the nasal pits in this figure ; they are 

 the small, dark, oval depressions lying between the 

 neural lube and optic vesicles. Compare Figure 15. 



Figure 15. — Lateral view of a specimen considerably more advanced. 

 The entire figure of the adult is quite well outlined ; 

 n. p. the nasal pit of the right side ; e, the developing 

 eye ; b, the rudiment of the balancer of the right side ; 

 n, the pericardial region, with heart partly showing 

 through ; bn, the branchial lobe, which is beginning to 

 divide into the three portions from which the branchiae 

 of this side will develop ; ba, lobe which gives origin 

 to the anterior limb ; vt, vertebrae ; pb, black pigment 



