270 TRANSACTIONS OF THE CANADIAN INSTITUTE. [VOL. I. 



somata. At this point the formation of zymogen granules begins in the 

 part of the cell next the lumen and it proceeds till the cell is filled with 

 them. As to the origin and mode of production of the zymogen granules 

 nothing is known. When secretion begins these granules disappear and 

 the nucleus now tends to return to the condition found in the exhausted 

 cell. 



My own observations coincide with those of Steinhaus. I may empha- 

 size here one or two points. The nucleus of the exhausted gland cell 

 stains readily and deeply with safranin, that of the cell in which the for- 

 mation of zymogen is going on vigorously, is colored deeply with hzemato- 

 xylin, while its plasmosoma takes readily the safranin. 



My explanation of this phenomenon is drawn from the results of my 

 observations on the formation of yolk in the ovarian ova of Necturus and 

 Rana, and a summary of these may therefore not be out of place here. 



In the nuclei of the developing ova at a certain stage the chromatin 

 is principally collected in the form of nucleoli at the periphery immedi- 

 ately under the nuclear membrane. These nucleoli are usually spherical 

 and they may, though not usually, or very much, vary in size. All the 

 chromatin of the nucleus is not so situated, for there are long threads 

 which at certain points in the granular karyoplasma unite at angles with 

 one another. At this stage yolk spherules are absent from the cell. If 

 now sections of such an ovary are stained with the indigo-carmine 

 stain of Shakespeare and Norris, the significance of the peripheral 

 nucleoli is determined. Such sections show here and there an ovum in 

 which the peripheral nucleoli are stained deep blue, while the remainder of 

 the nucleus and cell is stained red. In other ova, again, the peripheral 

 nucleoli and the karyoplasma are stained blue, the cell red, while in others 

 again the peripheral nucleoli are smaller, the whole ovum, with its yolk 

 spherules which now begin to be formed, is stained blue, or blue green. 



The origin of the substance which stains indigo-blue in this process is 

 certainly derived from the peripheral nucleoli, for it is possible to meet 

 with an ovum once in a while in which a portion of the karyoplasma in 

 the immediate neighborhood of and around each nucleolus is, like the 

 latter, stained indigo-blue, while the remainder of the karyoplasma is red. 

 The peripheral nucleoli generate a substance, therefore, which diffuses 

 gradually through the nucleus, then into the cell protoplasm, the point 

 in time of the latter occurrence corresponding with the formation of the 

 yolk spherules. The mode of origin is through a process of deposition 

 from the nucleus of a substance allied to chromatin in the cytoplasm. 



The diffusion of a substance produced from the nucleoli through the 



