360 



DYNAMICS OF HISTOGENESIS. 



Figs. 1 to 9. Sections of the epithelial tube representing one complete turn in 

 a dexiotropic rotation in a spiral manner of the mitotic division. The primary 

 type is the left-handed helix. Spiral path is directed upward toward the ileo- 

 cecal valve. Section 62 represents the head or apical end of the mitotic path. 

 Sections 55 and 54 represent the tail or basal end of the mitotic spiral path, mil, 

 mitosis; bm, basement membrane of the epithelial tube. Drawings are made with 

 the aid of a Spencer Camera lucida. Sections 54 to 62 are from Pig Embryo 19, 

 24 mm. in length (Creighton Embryological Collection). 



