PLATE A. 



1 



""") / 



L* 





6 



9 



V-A;- 5< 



M$S 



^v* *& 



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



CERCA DAMNIFICA. 



rc, accessory or sex chromosome; p, plasmosome; i, idiosome. 1 to 7, spermato- 

 gonia; 8 to 19, primary spermatocytes ; 20 to 26, secondary spermatocytes; 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 



