RELATION BETWEEN AMITOSIS AND MITOSIS. 1 67 



of the proliferating area from which this portion of the ducts will 

 develop. The axis of the developing duct corresponds to a line 

 drawn vertically through the middle of the figure. The nuclei 

 are just beginning to be affected by the conditions which produce 

 proliferation ; thus the figure represents approximately the earliest 

 stage at which this portion of the ducts is distinctly visible. 

 From the cord of cells in this lateral region both vagina and vas 

 deferens differentiate, but there is no distinction between them 

 until much later stages. 



Fig. 2 (PI. VIII.) represents a section similar to Fig. 1 of the 

 cord of cells from the same region at a somewhat later stage. 

 The nuclei are more numerous and amitoses are apparently more 

 frequent. At the right is one of the very rare cases of mitosis 

 observed in the development of the genital ducts. It will be 

 observed that it lies on the border of the region involved in pro- 

 liferation and the same is true of most other cases observed. 

 Not a single case of mitosis has been observed in the axial region 

 of the cell-cords from which the ducts arise and only six cases 

 of mitosis have ever been seen outside the ovaries and testes in 

 Moniezia expansa and M. plants sima, though extended search 

 for them has been made. 



Fig. 3 (PI. VIII.) is a section similar to Fig. I of the cord of 

 cells from which the vas deferens develops, taken from a point near 

 its upper or inner end where it does not adjoin the vagina. As 

 regards nuclear division this figure is very similar to the preced- 

 ing. On the right is shown one of the cases mentioned and 

 figured in earlier papers (Child, 'oya, 'oyb, 'ojd) where the two 

 parts of a nucleus which is apparently undergoing amitosis stain 

 differently. 



In Fig. 4 (PI. IX.) a transverse section of the vas deferens at a 

 somewhat later stage after the lumen has appeared is shown. 

 Amitotic nuclear divisions are still taking place, but apparently 

 less rapidly than in earlier stages, or else the nuclei increase in 

 size more rapidly between successive divisions. 



Fig. 5 shows a portion of a vas efferens near its junction with 

 others. Two cases of undoubted amitosis are visible. Fig. 6 

 is from the outer portion of the wall of the oviduct and includes 

 one case of mitosis besides several amitoses. 



