EXPLANATION OF PLATES 



All figures are drawn to the same scale except figure 29, which was drawn to 

 one-half the scale of the others. The drawings were all made at table level 

 with a Leitz camera lucida and with the use of Leitz ocular 6 and Leitz 2 mm. 

 apochromat N. A. 1.32 objective, draw tube set at 152 mm. With one-third 

 reduction in reproduction the magnification is thus 926 diameters (except figure 

 29). At all stages in the development of the spermatozoon size variations may 

 be noted. In most cases an average-sized representative of a particular stage 

 has been selected, but the figures will show some exceptions to this practice. 

 Only those cytoplasmic constituents which are essential to the discussion are 

 represented in the drawings; otherwise distinctions could not be expressed satis- 

 factorily with line drawings. Unless otherwise indicated the drawings are 

 made from sections 2 to 5 in thickness. 



PLATE 1 



EXPLANATION OF FIGURES 



1 Spermatogonial cell in division. The small dots in the cytoplasm in this 

 and the figures which follow represent mitochondria. 



2 Two cells at the beginning of the growth period. The nuclear cap is formed 

 of mitochondria. 



3 Three growing cells from a testicular cyst. 



4 Early growth stage showing genesis of extra-nuclear bodies (e.b.) and 

 vesicular bodies (o.b.). 



5, 6, 7 and 8 Successive stages in the growth period. Figure 7 shows the 

 first evidence of the striated layer (s.l.). 



ABBREVIATIONS 



(i.m., aggregating mitochondria 



(./)., cilia-like processes 



e.b., extranuclear bodies 



/., flagellum 



/.p., finger-form process 



g.c, gelatinous envelop 



i.e., invagination cavity 



i.t., inner tube 



mi., true mitochondria 



m.r., mitochondrial rin{ 

 n., nucleus 

 o.d., oil droplet 

 o.t., outer tube 

 pi., plasmosome 

 s.l., striated layer 

 v.b., vesicular bodies 

 z., zwischenkorper 



H6S 



