598 Transactions of the Society. 



XXI. — The lie-appearance of the Nucleolus in Mitosis. 

 By E. J. Sheppard. 



(Read April 19, 1911.) 



Plate XIX. 



Some time back I had the honour of reading before the Society a 

 paper upon " The Disappearance of the Nucleolus " in Mitosis. 



The subject of the present paper is upon its Re-appearance, and 

 it is my desire to bring before your notice some observations I have 

 made with regard to this equally interesting subject. 



The processes of staining, fixing, and other treatment of sections 

 and tissues adopted in the study of the above subject have been, 

 with the exception of two slight modifications, the same as men- 

 tioned in my previous paper upon "The Disappearance of the 

 Nucleolus." 



The two modifications mentioned are as follows : — 



First, the abandonment of the use of picric-formol for fixing. 



Second, a much longer time occupied in the mordanting and 

 hematoxylin staining baths. 



The fast was adopted because after repeated trials I came to 

 the conclusion that for work upon the subject of mitosis, preferable 

 results are obtained by the use of Flemming's, Lindsay Johnson's, 

 and Hermann's solutions. 



With regard to the second, that of mordanting and staining, I 

 have prolonged the immersion of sections in these baths for as 

 much as 36 hours in the former and 72 hours in the latter. This 

 seems to me to give the maximum degree of perfection with 

 regard to staining, and the highest resisting power obtainable to 

 the finest nuclear structures for their second iron or differentia- 

 tion bath. 



This applies to such Amphibia as the frog, triton and sala- 



EXPLANATION OF PLATE XIX. 



Fig. 1. — Loops in chromatin of daughter-nuclei before disappearance of inter- 

 zonal fibres. Hyacinthus. 



„ 2. — Loops in chromatin of daughter-nuclei. Hyacinthus. 



,, 3. — Re-appearing nuclei. Top daughter-nucleus with nucleolus well developed ; 

 chromatin not quite severed from nucleolus. Bottom daughter- 

 nucleolus not so fully developed, its lower left portion still fused with 

 chromatin. 



.. 4.— Loops in chromatin (telophase). Triton. 



„ 5. — Loops in chromatin (telophase). Salamander. 



