394 WALTER E. CAMP 



very similar condition, it will be recalled, was found in the 

 anlage of the gland. 



The newly formed outgrowth may remain connected and grow 

 en masse with the parent follicle, forming a branching tubule, 

 or may become pinched off, forming a new vesicle. The former 

 condition is more common when the buds arise from the ex- 

 tremities of the parent tubule. It is not unusual to find in these 

 cases three, or sometimes four, small sprouts arising from the 

 extremity of a single tubule (fig. 24, c, and fig. 26). Secondary 

 branching or dichotomous division of tubules does not occur. 

 A newly formed branch does not give rise to a new gland element 

 until it has become pinched off as a vesicle. 



The process of separation of the tubules is by simple con- 

 striction of its connection with the parent tubule. This process 

 can be found in all its stages, especially in the older embryos 

 where the tubules are more numerous. The connection of the 

 new branch, which presumably persists for some time, becomes 

 gradually larger as the tubule grows. At the outset of con- 

 striction, the wall of the branch at its connection gradually 

 grows in across the lumen of the junction (fig. 13). Usually 

 this ingrowth occurs on all sides, but if the branch is bent 

 upon the tubule it may occur only on one side. The constric- 

 tion or ingrowth of the wall is always accompanied by the sur- 

 rounding mesenchymal cells. 



The nuclei of the cells of the ingrowing walls have, at first, 

 a radial position with respect to the lumen. As the constric- 

 tion proceeds and the cells from the opposite walls fuse, the 

 nuclei become very much elongated and assume a position in 

 which their long axes are tangential to the lumen. Figures 13 

 and 14a, show that this change in the position of the nuclei is 

 not due to a rotation of either the nuclei or the cells, but results 

 simply from the inward migration of the cells. When the new 

 tubule or follicle becomes completely separated from the parent 

 tubule the nuclei are again found placed radially with respect to 

 the lumina (fig. 14o). Whether this change in the direction 

 of the axes of the nuclei is due to a rotation of these bodies 

 through an arc of 90 degrees, or whether it results from a change 



