Volume X. February, iSgS- Number 2. 



JOURNAL 



MORPHOLOGY. 



THE EARLY DEVELOPMENT OF AMBLYSTOMA, 

 WITH OBSERVATIONS ON SOME OTHER VER- 

 TEBRATES. 



ALBERT C. EYCLESHYMER. 



TABLE OF CONTENTS. 



PAGE 



Cleavage to Gastrulation 346 



1. Methods 346 



2. The Unsegmented Ovum 347 



3. Cleavage of Amblystoma 348 



4. Cleavage of Petromyzon 355 



5. Cleavage of Coregonus 357 



6. General Considerations 359 



Gastrulation to Closure of Neural Folds 366 



1. Formation and Closure of the Blastopore in Ambly- 



stoma 366 



2. Origin of the Mesoblast and Chorda 370 



3. Experiments 373 



4. The Embryonic Area 375 



5. The Primitive Streak and Groove 376 



6. The Epiblast and Mesoblast in Petromyzon 378 



7. Gastrulation and Fate of the Germ-Ring in Amiurus and 



LoPHius 3S1 



