Fig. 341. The development of Necturus maculosus. (A) Side view of egg 1 day 

 and 8 hours after deposition, showing second and third cleavage grooves. (B) Bot- 

 tom view of egg 6 days and 16 hours old. The crescentic blastoporal fold sharply 

 separates the large yolk-cells from the small cells of the blastodisk. (C) Bottom 

 view of egg 10 days and 10 hours old, showing large circular blastopore. (D) Top 

 view of egg 14 days and 4 hours old. Blastopore narrow. Beginning of neural-fold 

 formation, especially prominent anteriorly. (E) Top view of egg 15 days and 15 

 hours old. Yolk plug still visible. Neural folds prominent. Their posterior ends 

 extend to the blastopore. (F) Top view of egg 18 days and 15 hours old, with three 

 or four pairs of myotomes visible. Bight and left neural folds nearly meet (G). 

 Dorsolateral view of embryo 22 days and 17 hours old; length 8 mm.; 16 to 18 

 myotomes. (H) Side view of embryo 26 days old; length 11 mm.; 26 to 27 myo- 

 tomes. Eye, ear, nasal pits, and mouth well defined. (I) Side view of embryo 36 

 days and 16 hours old; length 16 mm.; 36 to 38 myotomes. (J) Side view of larva 

 49 days old ; length 21 mm. (K) Side view of larva 97 days old ; length 34 mm. (After 

 Eycleshymer and Wilson. By permission from "Biology of the Amphibia," by G. K. 

 Noble, copyrighted 1931. McGraw-Hill Book Co., Inc.) 



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