408 HARRY H. CHARLTON 



SUMMARY 



1. The male Lepisma domestica has three pairs of testes on 

 each side, each testis connected by a duct with the respective 

 vas deferens. 



2. The blind end of the testis contains the youngest stages. 



3. Primary spermatogonia are formed very early in life. 



4. Thirty-four chromosomes are present in the spermatogonia. 

 A chromatic nucleolus is present in the resting stage of the 

 spermatogonia. 



5. The growth stages follow the description given by Wilson 

 ('12). 



6. A planosome is seen in the resting stage of the sperma- 

 togonia appearing in the growth stages as a much larger body. 



7. One or two plasmosomes appear shortly after formation of 

 the spireme threads, and disappear later. 



8. There are eighteen chromosomes in the first maturation 

 division. The two idiochromosomes pass undivided to one 

 pole. 



9. The autochromosomes divide longitudinally in the second 

 division, while the idiochromosomes do not. Instead, they 

 separate, each spermatid receiving one idiochromosome. 



10. The form of the centrosome is changeable, but its almost 

 constant presence either in the shape of a granule or of a rod 

 indicates that it may be a permanent cell structure. 



11. A chromatic nucleolus is present in half of the spermatids. 



12. The nebenkern is formed from granular mitochondria, the 

 remains of the last and of two previous spindles. 



13. The axial filament grows from the end of the rod-shaped 

 centrosome which forms the acrosome. 



14. Another body, presumably derived from the nebenkern, 

 forms the middle-piece. 



15. The nebenkern, after separating out the spindle remains 

 and several accumulations of mitochondrial material, form a 

 vacuolated body which furnishes a sheath for the axial filament. 



16. The axial filament persists and forms the undulating 

 membrane of the mature spermatozoa. 



