602 



infrequent type of cell. Here a second direct nuclear division imme- 

 diately succeeds the first. The four still united nuclei appear to lie 

 in a clear space bounded by a delicate menbrane. The latter, however, 

 cannot be interpreted as the membrane of the original nucleus. Divi- 

 sion takes place not inside the nuclear membrane as described in 

 amitosis of certain forms (Moniezia, Child, 1907; chick blastoderm, 

 Patterson, 1911), but on it, the initial step apparently involving 

 its invagination (constriction). Figure 15 represents an unusually 

 wide cell, with an elongate oval vesicular nucleus undergoing hori- 

 zontal cleavage along a path distinctly marked by an intense chro- 

 ma ti city. 



Figures 16 to 24 represent a portion of the wall of a vas efferens 

 at a level characterized by columnar cells. In this particular section 

 including 205 nuclei, 45 were at various phases of amitosis. The very 

 abundance of such nuclei argues for an important role in cell multi- 

 plication in this tissue. The division stages are all final as concerns 





Figs. 13 to 15. Selected cells from another section of an efferent duct. In 

 13 the point of final separation of the daughter nuclei is shown as a darker circular 

 area within the lighter second nucleus. In 14 the two daughter nuclei are under- 

 going immediate fission. The four nuclei appear to lie in a clear space, the boundary 

 of which, however, is not the original nuclear membrane. Such multiple amitoses 

 are not infrequent. (They are especially common in tiie efferent ducts of the lobster 

 testis). In 15 the mitotic division is passing through the later stages. 



the nuclei and require no further comment apart from their descrip- 

 tion in the legends; but no cytoplasmic demarcations are yet discer- 

 nible. These cells show clearly termined bars and basal granules. 

 Below cells 18 and 23, and inside the basement membrane, are oval 

 nuclei of basal cells. No mitoses were seen among them though they 

 may possibly occur; nor indeed are amitosis to be found anywhere 

 in any type of cell of the epididymis. The basal cells grow upward 

 between the ciliated cells and become columnar (e. g. 24) and acquire 

 cilia. 



Figures 25 to 31 are selected cells from an adjacent section. In 

 lig. 27 the constriction has just begun at the upper pole of an oval 

 nucleus oriented with its long axis in the long axis of the cell. Figure 



