308 The American Naturalist. [April, 



Separation of chromatin segments. C. Fusion of chromatin 

 segments at each pole.. 7 and 8. Organization of the 

 daughter nuclei and formation of the cell plate. 9. The two 

 resulting daughter nuclei. 



Figs. 10-11. (Redrawn from Watase.— " Karyokenesis " Bio- 

 logical Lectures p. 168). Fig. 10. Nucleus dividing, showing 

 archoplasmic spheres; (a) centre of archoplasm; (c) cyto- 

 plasm. Fig. 11. Division of the archoplasmic sphere. 



Fig. 12. atie outline of nuclear division 



modeled from Guignard's description; (a) centrosome sur- 

 rounded by a hyaline circle ; (6) surrounding granular circle ; 

 (c) cytoplasm. 



Fig. 13. (Original). Diagramatic outline of the development 

 of the Acrasiese ; (a) spore ; (6) escaping mass of protoplasm ; 

 (c) swarm spore; (d) swarm spore preparing for division; (e) 

 dividing swarm spore; (/) completion of the division; (g) 

 Plasmodium; {h) sporangium. 



Fig. 14. (Original). Diagramatic outline of the plasmodium 

 formation, etc. in Myoxomycetes ; (a) swarm spores; {b) starting 

 of fusion ; (c) plasmodium ; (d) sporangium. 



Figs. 15-16. (Redrawn from Strasburger Bot. Zeit. xxxv, 

 (1877) Taf. xiii, fig. 14, f. and i.) Multiple conjugation of the 

 zoospores of Acetabularia mediterranea. 



Fig. 17. (Redrawn from Dod el-Port in Vines. Phys. Bot. p. 

 606) Planogametes of Ulothrix, one free, others in conjugation, 



Fig. 18. (Uedrawn from Strasburger) Reproduction of a moss 

 plant ; (a) arehegonium with enclosed egg cell ; (b) antherozooid. 



Fig. 19. (Redrawn after Berthold in Binet's Psychic Life of 

 Micro-Organisms p. 84) Planogametes of Edocarpus siliculosus. 

 (a-c) Differentiation of female planogamete ; (d) female piano- 

 gamete surrounded by males; (e-h) process of conjugation. 



Fig. 20. (Adapted from Gcddes and Thomson in Evolution 

 of Sex.) Diagram of the course of development of fecunda- 

 tion, (a) Adhesion of swarm spores into plasmodium, ex. 

 Acrasiese; (b) fusion of a warm spores into plusmodium, ex. 

 Myzomycetes; (c) multiple conjugation of planogametes, ex. 

 Acetabularia; {d) conjugation of two planogametes, ex. Ulothrix; 

 (e) conjugation of dimorphic notile cells, ex. Cutlcria; (/) 



