360 GEORGE A. BATES 



of the axis, which is parallel to the surface of the ectoderm, not 

 perpendicular to it, as it must be, if, in its division, it is to contrib- 

 ute a daughter-cell to the duct. He says: 



Am hinter Ende des Ganges sind hier drei Theilungsfiguren zu sehen. 

 Diejenige, welche sich unmittelbar an den Vornierengang anschliezt 

 und auf die es daher zunachst ankommt, ist ein Miitterstern, der so 

 gestellt ist, dass man auf ihn in der Richtung der Achse seiht; die Achse 

 steht also parallel zum Ektoderm, nicht senkrecht, wie sie stehen 

 mtisste, wenn die Figur beweisend sein sollte. Die beiden anderen 

 Theilungsfiguren sind, meiner Ansicht nach, irrelevant. 



Riickert, in his figures 35 to 41, shows several sections which 

 display much the same conditions as are presented in the cross 

 sections figured in the present paper, and in the light of the writer's 

 own observations and the repeated instances where the same rela- 

 tive position of duct and ectoderm have existed, it is difficult to 

 escape the conclusion that the same interpretation is inevitable 

 in both cases. So far as the mitotic figures are concerned it seems 

 certain that two of them are in the duct and one in the ectoderm. 

 All three of the cells are in metaphase, and the two in the duct are 

 so placed that the direction of division would be such as to pre- 

 clude the possibility of exchange of cells between ectoderm and 

 duct, even though the mitosis were in the ectoderm. This is 

 what Rabl meant, it would seem, although he considered only one 

 of the mitotic figures. 



Numerous mitotic figures are illustrated in my drawings, 

 several of which are of particular interest. Figure 35 shows a cell 

 in mitosis in the ectoderm, which is thinned out at one place and 

 the duct is attached to it just above this. The attachment is by 

 means of the peculiar clear protoplasm, before alluded to. In this 

 case it seems to have contracted and drawn the ectoderm out of 

 line so that the mitotic cell is deflected toward the anlage. It will 

 be readily observed that, if the method of preparation did not 

 make it possible to demonstrate clearly the outline of the cell and 

 the limiting membrane between the two layers, the structures 

 would appear to be continuous. It is true that the mitosis is in 

 metaphase, with the axis in the wrong direction for possible con- 

 tribution of a cell to the duct, but suppose the same conditions to 



