154 LOUISE B. WALLACE. 



EXPLANATION OF PLATES. 



All figures were drawn with the aid of a camera lucida under Bausch and Lomb 

 one twelfth oil immersion and Zeiss Comp. oc. 12. at table level and in the plates 

 are reduced about one eighth. 



All not otherwise specified are taken from Agalena navia. 



Abbreviations : a.c, accessory chromosome ; <?, mature spermatozoon ; b, degen- 

 erating cytoplasmic body; c, degenerating spermatid ; d, degenerating spermato- 

 zoon (?) ; y, yolk nucleus. 



EXPLANATION OF PLATE I. 



FIGS. I, 2. Spermatogonium. Metaphase. 



FIGS. 3, 4. Spermatogonium. Anaphase. 



FIGS. 5-7. Primary spermatocytes. Rest stage. 



FIGS. 8, 9. Primary spermatocytes. Contraction stage. 



FIGS. 10-12. Primary spermatocytes of growth period. Spireme not split. 



FIG. 13. Primary spermatocyte. Spireme thread longitudinally split. 



FIG. 14. Primary spermatocyte. Cross-section of split spireme. 



FIGS. 15-17. Primary spermatocytes. Split in spireme thread widens. The ac- 

 cessory chromosomes conjugate. 



FIG. 18. Primary spermatocyte. Cross-section of split spireme and conjugated 

 accessory chromosomes. 



