STUDIES IN THE LIFE HISTORIES OF EUGLENIDA

IV. A COMPARISON OF THE STRUCTURE AND DIVISION OF DISTIGMA PROTEUS EHRENBERG AND ASTASIA DANGEARDI LEMM. A STUDY IN PHYLOGENY

¹ Research Zoölogist, Dept. Water and Sewage Research

1. The structures of living and stained Distigma proteus Ehbg. and Astasia dangeardi Lemm. are shown and compared.

2. Formation of yellow pentagonal cysts is noted for Distigma.

3. Distigma has 16 chromosomes, Astasia has 12. In both animals they are elongate and somewhat beaded. They form irregular metaphase plates and by a separation of halves of the longitudinal chromosomes, surround the endosome with a cordon of rod-like chromosomes.

4. The final parting of the two daughter chromosomes is as a rule at one end, but it simulates a transverse break.

5. Individual chromosomes may persist in the nuclei of daughter cells of D. proteus even after separation, but in A. dangeardi reorganization of the nuclei is complete by the time the cells separate.

6. Mitosis is anastral in these organisms, there being no centrioles, asters, or spindles.

7. The endosome seems to take the place of the spindle.

8. The blepharoplasts do not function as division centers, but do divide, or bud off daughter blepharoplasts.

9. One daughter cell gets an old kinetic complex (flagella, blepharoplasts) and the other part gets new kinetic organelles, the one or two flagella growing out from the blepharoplasts.

10. It is suggested that the Euglena with a bifurcated flagellum on which is a discoid thickening, and the Astasiidæ having a bifurcated flagellum with no discoid thickening came from an ancestral form whose flagellum did not have two roots, while the complete splitting of the bifurcated flagellum of the Astasiidæ gave rise to the Heteronemideæ, with two or more non-bifurcated flagella.