350 



CELL-CHEMISTRY AND CELL-PHYSIOLOGY 



the tg^ contains accumulations of similar granules, which extend 

 inward in dense masses from the nutritive cells to the germinal vesi- 

 cle, which they may more or less completely surround. The latter 

 meanwhile becomes amoeboid, sending out long pseudopodia, which 

 are always directed toward the principal mass of granules (Fig. jj). 

 The granules could not be traced into the nucleus, but the latter grows 

 rapidly during these changes, proving that matter must be absorbed 

 by it, probably in a liquid form.^ 



Among other facts pointing in the same direction may be mentioned 

 Miss Huie's ('97) observations on the gland-cells of Drosera, and those 

 of Mathews ('99) on the changes of the pancreas-cell in Nect7irus. 

 Stimulus of the gland-cells in the leaf of Drosera causes a rapid 

 exhaustion and change of staining-capacity in the cytoplasm. During 

 the ensuing repose the cytoplasm is rebuilt out of material laid down 

 immediately around the nucleus, and agreeing closely in appearance 

 and staining-reaction with the achromatic nuclear constituents. The 

 chromatin increases in bulk during a period preceding the constructive 

 phase, but decreases (while the nucleolar material increases) as the 

 cytoplasm is restored. In the pancreas-cell, as has long been known, 

 the "loaded" cell (before secretion) is filled with metaplasmic zymo- 

 gen-granules, which disappear during secretion, the cell meanwhile 

 becoming filled with protoplasmic fibrils (Fig. 18). During the ensu- 

 ing period of "rest" the zymogen-granules are re-formed at the 

 expense of the fibrillar material, which is finally found only at the 

 base of the cell near the nucleus. Upon discharge of the secretion 

 (granule-material) the fibrillse again advance from the nucleus toward 

 the periphery. Mathews shows that many if not all of them may be 

 traced at one end actually into the nuclear wall, and concludes that 

 they are directly formed by the nucleus. 



Beside the foregoing facts may be placed the strong evidence 

 reviewed at pages 156-158, indicating the formation of the yolk-nu- 

 cleus, and indirectly of the yolk-material, by the nucleus. All of these 

 and a lars^e number of other observations in the same direction lead to 

 the conclusion that the cell-nucleus plays an active part in nutrition, 

 and that it is especially active during the constructive phases. On the 

 whole, therefore, the behaviour of the nucleus in this regard is in har- 

 mony with the result reached by experiment on the one-celled forms, 

 though it gives in itself a far less certain and convincing result. ^ 



1 Mention may conveniently here be made of Richard Hertwig's interesting observation 

 that in starved individuals of Actinospluvriwu the chromatin condenses into a single mass, 

 while in richly fed animals it is divided into fine granules scattered through the nucleus 



('98, p. 8). 



- Loeb ('98, '99) makes the interesting suggestion that the nucleus is especially con- 

 cerned in the oxydative processes of the cell, and that this is the key to its 7-dle in the syn- 

 thetic process. It has been shown that oxydations in the living tissues are probably 



