364 GENERAL EMBRYOLOGY 



SUMMARY OF THE CHIEF MORPHOGENETIC PROCESSES 

 I. Cell division and growth throughout the layer or disc, resulting in 



(a) Increase in thickness. 



(b) Increase in extent. 



(c) Increase in both thickness and extent. 



II. Cell division and growth localized in restricted areas of the layer 



or disc. 



A. Cells remain related and in continuity 



(a) Increasing in thickness. 



1. Radially formation of buds < t 



| hollow. 



2. Chiefly in one axis formation of strands ] j/- i * 



(6) Increasing in extent. 



(Dilation. 

 Invagination. 

 Evagination. 



(Groove. 

 Folds. 

 Tube (strand secondarily). 



B. Cells become separated to a varying degree. 



f Immigration 1 with corresponding 

 (a) Migration < -^ . ,. ; ,. . , . j ,,. 



[ Emigration J thickening and thinning. 



(ft) Rearrangement. 



(c) Delamination (sometimes preceded by thickening). 



(d) Fusion. 



III. Resorption. 



(a) Accompanying a process of perforation. 

 (6) Disappearance (degeneration). 



IV. Changes in cell form and size. 



(a) Thickening. 

 (6) Thinning. 



REFERENCES TO LITERATURE 



CERFONTAINE, P., Recherches sur le developpement de PAmphioxus. 



Arch. Biol. 22. 1906. 

 DAVENPORT, C. B., Studies in Morphogenesis. IV. A preliminary 



Catalogue of the Processes concerned in Ontogeny. Bull. Mus. 



Comp. Zool. Harvard Coll. 27. 1896. 

 EYCLESHYMER, A. C., The Formation of the Embryo of Necturus, with 



Remarks on the Theory of Concrescence. Anat. Anz. 21. 1902. 

 GREIL, A., Ueber die erste Anlage der Gefasse und des Blutes bei 



