PLATE A. 



;'C I 



* 



, * " - * 



, ', * 



- - ' 



6 



A 



itr 



9 



12 



PLATES A, B, AND C. SUCCESSIVE STAGES IN THE SPERMATOGENESIS OF SCHISTO- 



CERCA DAMNIFICA. 



x, accessory or sex chromosome; p, plasmosome; i, idiosomo. 1 to 7, sj)cnii:it<p- 

 gonia; 8 to 19, primary spermatocytes ; 20 to 26, secondary spcrmatocytcs; 27 to 30, 

 spermatids, differentiating (31 to 35) into the spermatozoon (36). 10, synapsis 

 stage; 18 and 24, metaphase plates of chromosomes; 6 a, diagram of a longitudinally 

 split univalent chromosome from the metaphase plate of a spermatozonial mitosis; 

 16b, diagram of a bivalent chromosome, in tetrad condition, from the metaphase 

 plate of the first maturation spindle, undergoing the reduction division; 23c, longi- 

 tudinally split univalent chromosome entering the second maturation spindle for the 

 equation division. (Flemming fixation; iron-hematoxylin stain.) X 1750. 



465 



