230 Mr W. Gardiner, On the constitution of Callus. [Mar. 16, 



the fact that it is soluble, and it was hence a matter of interest to 

 see whether, in the case of other ferment actions produced by 

 similar organisms, also containing a soluble ferment, this ferment 

 is similarly retained within the cell protoplasm. Working with 

 ordinary yeast (Torula cerevisiae) the author finds that at no 

 time during an active fermentation is any invertin to be found in 

 the fluid surrounding the cells. In this case as in the former the 

 ferment is retained by the cells. Experiments were described in 

 proof of the above statement. The invertin is not used up during 

 the change which it produces, neither do the yeast-cells destroy it 

 during their growth and activity. This is shewn by the facts that 

 if cane-sugar be inverted by a solution of invertin, this same 

 solution is again capable of inverting a further portion of cane- 

 sugar, and that if some invertin be added to yeast, and an active 

 fermentation then carried on with this yeast, then the invertin 

 can be recovered from the fluid surrounding the cells. 



It was suggested that the retention of the ferment by the cells 

 in the above cases is due to the fact that, unlike animal cells, the 

 Torulae are inclosed by a complete cellulose envelope which is not 

 broken up at the death of the cell, and that since all known 

 ferments though soluble are not diffusible, therefore even after 

 the death of the cell the ferment is retained in the dead cell- 

 substance. If the cells are treated in such a way as to break up 

 the cellulose envelope then the soluble ferments are capable of 

 being extracted with water. 



The outcome of the experiments shews that the ferment action 

 of these organisms is carried on in their protoplasm and not in the 

 fluid surrounding them by the excretion of every soluble ferment. 



(2) On some points in the anatomy of Nebalia. By G. Weldon, 

 M.A. 



(3) Observations on the constitution of Callus. By Walter 

 Gardiner, B.A. 



The author remarked that perhaps no structure had given rise 

 to so many differences of opinion as the callus of sieve-tubes. So 

 far as the question of its derivation was concerned there could be 

 little doubt that the views of Bussow and Strasburger, who 

 regarded it as being derived from the protoplasm, were right, and 

 that Wilhelm and Janczewski's view (as to its derivation from the 

 mucilaginous degeneration of the cell-wall) could not be main- 

 tained. While from its high organisation it seemed almost im- 

 perative to regard it as being formed in connection with, and 

 through the agency of, living protoplasm, yet the very early dis- 

 appearance of the nucleus and the scant quantity of the dying- 

 protoplasmic contents threw some doubt upon this assumption. 



