Studies on Chromosomes. 



393 



spermatogonial "chromatin-nucleoli" may either conjugate at the 

 period of general synapsis to form a bivalent body or may remain 

 separate as univalent bodies. As already pointed out, it was 

 probably this interpretation that led him to conclude that the 

 first division in these forms might show either seven or eight 

 chromosomes. But the later stages observed in Brochymena 

 give conclusive evidence that even though such a primary synapsis 



* :\ i i 



09 m 







o 



FIG. 7. 



Brochymena, Trichopepla. a-n, Brochymena, o-r, Trichopepla; a, b, idiochromosomes and plas- 

 mosomes, from early growth-period; c-g, condition of the idiochromosomes in middle and late growth- 

 periods; h, prophase of first division, showing idiochromosome-tetradj i, j, two stages, one following 

 and one preceding the last, in the division of the bivalent chromosome-nucleolus; k, metaphase-group, 

 first division; /, metaphase-group, second division; tn, side view, second division, showing idiochromo- 

 some-dyad and two other chromosomes; n, spermatogonial metaphase-group; o, metaphase-group, first 

 division, Trichopepla; p, spindle of second division in lateral view; q, r, sister-groups, late anaphase of 

 second division. 



