EXPLANATION OF PLATE I. 



All drawings were carefully outlined with a camera lucida and the details filled 

 in afterwards. For all the figures except 22 a Leitz y 1 ^ objective and a Zeiss ocular 

 1 8 was used. The reduction is approximately f giving a final magnification of 2,900 

 diameters. 



All the figures are taken from Gryllus domesticus except 22 and 24 from G 

 assimilis and 36 from Scapteriscus didactylits. 



The drawings are all numbered as nearly as possible in the order of the stages ot 

 development represented. Figs. 18, 19 and 22 are exceptions. 



In all figures x = accessory chromosome, n = nucleolus. 



FIG. i. Polar view of equatorial plate of a spermatogonial division. Accessory 

 bent into a U. 



FIG. 2. Idem. Accessory stretched out. The numbers indicate the probable 

 pairs of chromosomes. 



FIG. 3. Side view of spermatogonial spindle, the chromosomes just separating. 



FIG. 4. Early stage of growth period. Accessory adherent to one side. The 

 cell wall as in many other cases is not drawn as a definite line, because it is in many 

 cases not visibly differentiated by the stain and the exact limits between cells can 

 not be made out. 



FIG. 5. Later growth period. The chromatin in loops of spireme. 



FIGS. 6 AND 7. Later stages of the spireme. The chromatin still more or less in 

 loops. The accessory and nucleolus in juxta-position. Accessory in 6 lies in reality 

 against wall. 



FIG. 8. Later than above. One chromosome forms a ring. Accessory and 

 nucleolus at almost opposite sides of the nucleus. 



FIG. 9. Fragment of cell showing longitudinally split chromatin rods. 



FIG. 10. Chromatin somewhat more diffused. Accessory and nucleolus lie 

 together, but latter very pale in color. 



FIG. ii. Late prophase, the accessory dense and with smooth contour. Ordinary 

 chromosomes somewhat granular and with ragged contour. Chromosome 6 was 

 drawn from next section. 



FIG. 12. Polar view of very late prophase or metaphase of first spermatocyte 

 spindle. Chromosomes lie at different levels. 



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