282 J. E. S. MOORE. 



DESCRIPTION OF PLATES 15 & 16, 



Illustrating Mr. J. E. S. Moore^s paper on " Some Points in 

 the Origin of the Reproductive Elements in Apus and 

 Branchipus." 



PLATE 15. 



a = Pseudosomes. c = Centrosomes. d = Dictyosomes. da = Stages 

 intermediate between dictyosomes and pseudosomes. 



Figs. 1 — 5. — Stages in first division, from the resting cells to the formation 

 of chromosomes. Flemming's fluid and gentian violet, a. Pseudosomes. 



Figs. 6 and 7. — Formation of the chromosomes. 



Fig. 8. — Cell showing the breaking down of the nuclear membrane. 



Figs. 9 and 10. — Two spermatocytes, with nearly the same stage of early 

 spindle figure, da. Bodies intermediate between pseudosomes and dictyo- 

 somes. 



Fig. 11. — Transverse optical section of equatorial plate; fine strands of 

 protoplasm connecting the chromosomes to the exterior network. 



Fig. 12. — Cell a little later, in which the centrosomes have appeared. 



Fig. 13. — Older cell, in which the spindle figure seen in section is break- 

 ing down, and in which numerous bodies have appeared on the surface 

 dictyosomes. 



Fig. 14. — Final division of same. 



Fig. 15. — Secondary cell. 



Fig. 16. — Spermatozoa. 



Fig. 17. — Group of three spermatocytes in division, with numerous (d.) 

 dictyosomes and (c, c, c.) centrosomes. 



Fig. 18. — Figures produced by the growth of bubbles in a fine froth. 



Fig. 19. — Spermatocytes, showing the breaking down of the nuclear area. 



Fig. 20. — Foot-cell in akinetic division. 



Fig. 21. — Portion of spermatic epithelium, with various stages of sperma- 

 togenesis. F. c. Foot-cells. Sp. Spermatocytes and spermatozoa. 



Fig. 22. — Spermatocytes in division, showing the extreme position of the 

 centrosomes. 



Fig. 23. — Ditto, showing the early formation of the dictyosomes round a 

 spreading clear space. 



