PLATE 1 



EXPLANATION OF FIGURES 



1 Posterior segments, ventral surface, of male Lepisma domestica. X 20. 



2 Posterior segments, ventral surface, of female Lepisma domestica. X 20. 



3 Testes of one side showing connection with vas deferens and seminal vesicle. 

 X 20. 



4 Spermatogonium, surface view, showing resting condition of nucleus and 

 the attraction sphere. 



5 Prophase of spermatogonium. 



6 Metaphase plate early spermatogonium. Thirty-four chromosomes joined 

 by linin threads. 



7 Telophase spermatogonia showing persistent spindle remains. 



8, 9, 10, and 11 Nuclei of spermatogonia decreasing in size with each division. 

 12 Spermatogonial metaphase from the side. Centrosome as single granule at 

 poles. 



13, 14, and 15 Resting stages spermatogonia to show idiochromosomes. 



16 Spermatogonium showing the breaking up of the idiochromosomes. 



17 Beginning of growth period. Idiochromosomes reformed. 



18 Spindle remains from spermatogonium with two centrosome granules. 



19 Same as the preceding from early growth period with V-shaped centro- 

 somes. 



20 Centrosome rods with granules at their ends, before division. Plasmosome 

 and idiochromosome loops. 



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