No. I.] SPERMATOGENESIS OF BATRACHOSEPS. 117 



All the above chromosomes are copies from actual chromosomes and not dia- 

 grammatic. 



Figs. 121 and 122. The heterotypic mitosis by equation division. A diagram- 

 matic representation of the development of leaders of an auxocyte into chromo- 

 somes, their splitting and equation, in a progressive series from a to /. a, two 

 leaders connected by a divided chromoplast, the latter marked c. Numerous 

 chromomeres on the leaders, each with several chromioles. b, the same two 

 leaders, the chromomeres having contracted into a smaller number, each chromo- 

 mere having more chromioles, w'hich latter have now been arranged in two 

 parallel rows in each chromomere. This is the beginning of the stage in which 

 the leader splits, c, the same two leaders, but which have now split into four 

 leaders, each one of which will become a single chromosome in the daughter- 

 nucleus. The two halves of one leader form the bretzel-shaped chromosome. 

 Observe that the chromomeres have again separated and become smaller, d, the 

 same two leaders, the chromomeres having contracted anew, the whole leader 

 having shortened, e, the same two leaders, which have yet more shortened, and 

 the chromomeres have contracted into a smaller number ; the two chromoplasts 

 are seen at the junction of the two leaders. /, a single leader which has become 

 separated through the division of the chromoplast. It now forms a perfect bretzel- 

 shaped chromosome, consisting of two prongs connected by a dividing chromo- 

 plast. The two prongs of the leader have crossed each other and thus formed 

 the bretzel. _^ to ,^ are various forms of bretzel chromosomes, some of which 

 have their free ends overlapping, while two of them have the ends actually grown 

 together. /, a chromosome which has just undergone equation division. The 

 parting has taken place through the chromoplast ; c c, the two ends which were 

 grown together, are yet united by two fine threads of chromoplasm. m, two 

 chromosomes in the confluent umbrella stage, with several endochromatic 

 granules. 



XIII. STAINS, FIXATIVES, OPTICAL APPARATUS, etc. 



Congo, No. 1209, The Substantive Colors Co. Actien Gesellschaft fiir Anilin- 

 Fabrication. 



Thionin, Cogit & Co., Paris. 



Rutheniumroth, Dr. G. Griibler & Co., 200, Leipzig. 



Iridium Chloride, Merck & Co., Darmstadt, Germany. 



Apochromat No. 412, 2 mm., Apert. i. 40, Homog. Immers. Carl Zeiss, Jena. 



Apochromat No. 262, 3 mm., Apert. i. 40, Homog. Immers. Carl Zeiss, Jena. 



All the chemicals and optical apparatus furnished by Charles C. Riedy, San 

 Francisco, Cal. 



