250 Kn'osHi jiAsn. 



EXPL.\isATIOX OF PLATES. 



All figures were drawu with aid of a camera-luoida, us-iag a Zeiss 1.5 mm. apochromatic 

 objective and compensatiug ocular no. 12, excep. figs. 130, 133 which were drawn with Zeiss 3 mm. 



apochromatic objective and compensating ocular nj. ü All ihe figures on PI. IV, V, VI, VII, 

 figures 82-81 on PI. VIII, and figures 126-144 on PI. X are from mou.se. Th'-se in PI. IX. 

 figures 85-102 on PI. VIII and figs. 145-151 arc from rabbit. 



PL.VrE TV. 



All the figures drawn from mouse. 



Fig 1. Spermatogonium in resting stage, showing chromatin masses and nucleolus. 



Fig. 2. Spermatogonium in early prophase, showing m:my chromatin rods. 



Fig. 3. Spermatogonium in late prophase. 



Figs. 4, 5. Polar views of metaphase plates of spermatogonia, showing forty chromosomes. 



Fig. 6. Polar views of metaphase of spermatogonium, showing mitochondrial granules. 



Fig. 7. Side view of metaphase of sijermatogonium. 



Fig. 8. Side view of anaphase of spermatogonium. 



Fig?. 9-10. Chromosomes of spermatogonia arranged according to their area, showing pairs 

 of chromosomes and two special chromo3omes. 



Figs. 11-12. Chromosomes of spermatogonia arranged according to their form. 



Fig. 13. Chromosomes of anaphase of first reduction division, showing jjairs of chromo- 

 somes and two special chromosomes. 



Fig. 14. Side view of late anaphase of spermatogonium. 



Fig. 15. Leptott'ne stage of spermatocyte. 



Figs. 16, 17. Spermatocytes in synaptic st.oge, showing mitochondrial granules. 



Fig. 18. Spermatosyte in late synaptic st.age. 



Figs. 19, 20. Spermatoaytes in pastsyuairtic stage, showing nucleoli. 



PLATE V. 



All figures are from mouse. 



Fig, 21. Spermatocyte in post-synaptic s'agc, showing chromatoid body. 



Figs. 23-25. Spermatocytes in late jxjät-synaptic st.age, showing nucleoli, chromosome nucleoli 

 and chromatoid bodies. 



Fig. 26. Spermatocyte in late post-synaptic sta^e, showing mitochondriixl granules. 



Fig. 27. Spermatocyte in late lost-synaijlio stage, showing change of staining capacity of 

 chromatin spiremes. 



Figs. 28-33. Spermatocytes in ])ro[>hase of first di%-ision, showing various ring-shaped 

 chromosomes. 



Figs. 31-33. Polar views of early metaphase of first division, showing formation of tetrals 



