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N. M. Stevens 



DESCRiPTiOiNf OF Figures 



The figures were all drawn with camera lucida, Zeiss 1.5, oc. 12. 



Lettering on figures 



p = plasmosome. X2 = smaller heterochromosome. 



X = heterochromosome pair. 5 = division product of X2. 



xi = larger heterochromosome. 



Fig. I Nucleus of resting spermatogonium. (H,) 



Figs. 2 and 3 Spermatogonial equatorial plates, 24 chromosomes. (Ei*) 



Fig. 4 Spermatogonial equatorial plate, 24 chromosomes. (Hi*) 



Fig. 5 Synizesis stage. (H,) 



Fig. 6 Transition stage from synizesis stage to spireme stage. (Hi) 



Fig. 7 Later transition stage (E2) 



Fig. 8 Early growth stage, showing heterochromosome (x) and two plasmosomes. (Hi) 



Fig. 9 Later growth stage. (Hi) 



Fig. 10 Similar growth stage, showing vacuolated heterochromosome (v). (E2) 



Fig. II Growth stage showing the bivalent heterochromosome (jf). (H2) 



Fig. 12 Various forms of the heterochromosome from same cysts as Fig. 7 and Fig. 1 1. (H2 and Eo) 



Fig. 13 Early prophase showing split segments. (E2) 



Fig. 14 Similar stage showing the daughter segments separated and twisted. (Ei) 



Fig. 15 Later stage showing loop-form of segments. (Ei) 



Fig. 16 Section of a nucleus containing three different prophase stages, split segments, V-shaped 

 chromosomes, and twists. (E2) 



Fig. 17 Slightly later stage, showing U's and twists. (E2) 



Fig. 18 Various prophased forms, stage of Fig. 17. (E2) 



Fig. 19 Latei stage, showing U-shaped chromosomes and the heterochromosome Jf. (H,) 



Fig. 20 Later stage, showing U's and dumb-bells, x in outline above the U-shaped chromosome. 

 (H,) 



* Hi and H2 = Helgoland material; Ei and E2 = Eisenach material. 



