278 Mary A. Bowers. 



III. Miscroscopic changes : 



J. From earliest differentiation of the hirval epithelium two kinds 

 of cells may be distinguished, the principal cells and the basal giant 

 cells. 



2. The principal cells form the temporary, larval epithelium. 

 Degenerative phenomena begin to appear in these cells about two 

 weeks before the breaking through of the fore legs; they are coin- 

 cident with the shortening and narrowing of the intestine. 



3. As degeneration begins in the principal cells, the giant cells 

 become active, increase in size, divide mitotically, and form syncitia. 



4. These syncitia form cysts, hollow spheres. The nuclei then 

 become oriented, their long axes radiating from the center, and cell 

 walls form, making a single layer of columnar epithelium. 



5. The cysts break open on the side toward the degenerating 

 epithelium, unite with each other and form the definitive epithelium. 



6. "With the final muscular contraction, the degenerating epithelium 

 is pinched off into the lumen of the alimentary tract and eliminated 

 through the anus. 



PAPERS REFERRED TO. 



1. Babak, E. Ueber den Einfluss der Nahrung auf die Lange des Darm- 



kanals. Biolog. Centralbl., Bd. 23, 1903, pp. 477-483. 



2. Babak, E. Experimentelle Untersnchungen iiber die Variabilitat der 



Verdauungsrohre. Arch. f. Entwickl.-mechanik d. Organismen, Bd. 

 XXI, Heft 4, 1906, pp. 611-702. 



3. Bataillon, E. Recherches anatomiques et experimentales sur la meta- 



morphose des Amphibiens Anoures. Ann. Univ. Lyon, T. II, Fasc. T, 

 1891, pp 1-123, 6 pis. 



4. BizzozEBO. Ueber die schlauchformigen Driisen des Magendarmkanals 



und die Beziehungeu ihres Epithels zu dem Oberflachenepithel der 

 Schleimhaut. Arch. f. mikr. An., Bd. XL, 1892, pp. 325-375, taf. 18-19. 



5. Cannon, W. B. The Movements of the Intestines studied by means of 



the Rontgen Rays. Amer. Journ. Physiol., Vol. 6, No. 5, 1902. 

 0. DuESBERG. Contribution a I'etude des ph6nom&nes histologiques de la 

 metamorphose chez les Amphibiens Anoures. Arch. d. Biol., T. XXII. 

 Fasc. I, 1906, pp. 163-228, pis. 10-11. 



7. Kingsbury, B. F. The Regeneration of the Intestinal Epithelium in the 



Toad (Bufo lentiginosus Americanus) during Transformation. Trans. 

 Amer. Micr. Soc, XX, 1899, pp. 45-48. 



