TRANSACTIONS OF SECTION K. 1067 



and ultimately becomes again basophil. The changes in the nucleus comprise — 

 (1) those of the nuclear chromosomes, (2) those of the nuclear plasm, and (o) 

 those of the nucleoli. In the resting cell the nuclear chromatin is scanty, but 

 immediately after feeding it commences to increase, till in twenty to thirty hours 

 large segments are formed as in mitosis. During recuperation the segments again 

 diminish. The eosinophil nucleoli are large in the resting cell ; they diminish after 

 feeding in direct proportion to the increase of the basophil chromatin, and finally 

 enlarge when the chromatin segments diminish. 



Peptone is absorbed much more rapidly than egg-albumin, and produces in one 

 hour changes similar to those effected by egg-albumin in twenty to thirty hours. 



Globulin also produces changes in twenty-four hours, but to a less marked 

 degree than egg-albumiu. Food passes into the tentacle between the lateral walls 

 of the cells, and secretory products pass through the apical walls, thus producing 

 an appearance of striae in the food which is in contact with the tentacles. 



Fibrin is digested slowly, and changes similar to but generally less pronounced 

 than in egg-albumin are seen. 



Milk is absorbed rapidly and completely. The morphological changes are less 

 marked than with any of the above-mentioned foods. The cell plasm remains 

 basophil throughout. 



Nuclein produces almost no effect; the tentacles do not bend in, and do not 

 secrete more copiously than before. No cytological changes are produced except 

 Tery slight vacuolation of the cell plasm. All the colour reactions are the same 

 as those of controls. 



Nucleic acid produced rapid bending in of the tentacles, and extremely copious 

 secretion. The leaves reopen in one to three days, and although the quantity of 

 nucleic acid given is not perceptibly diminished, there are great histological 

 changes, consisting in an almost complete disappearance of the cytoplasm (which 

 remains basophil throughout), and of the nucleoplasm. The basophil chromatin 

 segments remain unaltered. 



Calcium phosphate produces appearances very similar to those after feeding 

 with egg-albumin, but the cytoplasm remains basophil. 



Control leaves, after the application of all the above substances, reopened in a 

 perfectly healthy condition, as determined by their naked-eye appearances while 

 living, and their microscopic structure after fixing by different methods. 



2. Theoretical Calculation of an Osmotic Optimum. 

 By Professor Dr. L. Errera (Brussels). 



Recent researches made by Dr. F. Van Rysselberghe in the Botanical Institute 

 of Brussels have shown that vegetable cells generally answer an osmotic stimulus 

 by an appropriate osmotic reaction, and that the relation between stimulus and 

 reaction follows, within wide limits, the ' law of Weber.' Hence results the possi- 

 bility of predicting the existence and value of an osmotic optimum. 

 Let n be the normal osmotic pressure in a given cell ; 



X the osmotic pressure of an external solution applied as stimulus ; 

 -R the reaction, i.e. the change in the osmotic pressure of the cell in response 

 to this stimulus. Then one has, according to Weber's law : 



Jc = c log - (c and s being constants). 

 s 



The total value of the osmotic pressure in the cell is of course M + n, and its 

 excess over the pressure of the surrounding solution is, 



1/ = Ii-i-7l — X, 



or 7/ = clog - +n—x. 



•^ ° s 



It is easy to find by differentiation that this excess has a maximum value wheit 

 x = c log e (e being the basis of the Naperian logarithms = 2,7182818 . . . ). 



