XXXVI] CELL-DIVISION 287 



The double star, in which the secondary chromo- 

 somes have separated from one another, and have 

 moved towards the poles. 



The secondary tangle, in which the secondary 

 chromosomes have united more or less completely by 

 their ends, and by transverse connecting threads ; the 

 cell-substance may show a slight constriction. 



The secondary nuclei, having the character of 

 resting nuclei, and with the cell-substance between 

 them more or less constricted. 



In the salamander a thin-fibred tangle precedes the thick-fibred 

 tangle. 



Indications of the cell-spindle may be seen, but this structure will 

 not be very distinct. 



2. Stain sections of salamander (mercuric chloride ; cut 3 to 

 6/i thick in paraffin) by the iron-hsematoxylin method. 



Prepare the sections for staining on the cover-slip (cp. p. 46). 



Place in 2*5 p.c. aqueous solution of violet crystals of iron- 

 alurn for 4 to 8 hours, wash well with water, place in Weigert's 

 hsematoxylin (see p. 289), diluted with an equal volume of 

 distilled water. 



Wash in 1 2 litres of water ;. place in a little 2*5 p.c. iron- 

 alum, moving the cover-slip about ; when the sections are 

 sufficiently decolourized, put back in the water to wash. 



Dehydrate, clear with xylol, mount in balsam. 



Note the two small particles, the centrosomes, on one side of 

 some of the resting nuclei, and on opposite sides in the star and 

 later stages of the dividing nuclei. Indications of spindle fibres 

 will probably also be seen. 



3. Stain, as in 2, sections of red medulla of bone hardened 

 in mercuric chloride. Some of the leucocytes may show two 

 centrosomes and a centrosphere. 



