551 



XV. — The Disappearance of the Nucleolus in Mitosis. 

 By E. J. Sheppard, F.E.M.S. 



(Read April 21, 1909.) 

 Plate XIX. 



Having made a great number of careful observations of fixed cells 

 in the epidermis of tadpole, and comparing these with cells in 

 growing root tips of Hyacinthus, the following remarks resultant 

 from same may be of interest. 



The fixing solutions used were as follows : — 



1. Flemming's. 



2. P. Bouin's picro-formol (slightly modified). 



3. Lindsay Johnson's platinic mixture. 



The formulas, etc., for these solutions will be found in Bolles 

 Lee's Vade Mecum, sixth edition, but the modification of Bouin's 

 picro-formol used and made by me was the following : — 



Saturated solution picric acid . . . . 150 c.cm. 



Distilled water . . . . . . . . 150 „ 



Acetic acid . . . . . . . . 2 „ 



Formol . . . . . . . . . . 30 „ 



This formula I used more particularly for fixation of tadpole 

 cells, but it is difficult to say whether better results were obtained 

 thus than with the use of Flemming's or Lindsay Johnson's 

 solution. I am inclined to give preference to either of the latter. 

 The reason for reducing its strength was because I found that 

 better differentiation or clearness was given than with the stronger 

 formula. 



The methods of staining adopted were Heidenhain's iron- 



EXPLANATION OF PLATE XIX. 



Fig. 1. — Allium. Peripheral contraction of nucleolus and association with chro- 

 mosomes. 



,, 2. — Hyacinthus. Fine processes extending from nucleolus to chromatin. 



„ 3.— Ditto. Ditto. 



„ 4. — Ditto. Late disappearance of nucleolus closely associated with chro- 

 mosome. 



„ 5. — Ditto. Ditto. 



„ 6. — Allium. Late disappearance of nucleolus closely associated with chro- 

 mosome. 



•1 P 2 



