TRICHOMONAD FLAGELLATES. 359 



13. During mitosis the organelles are subject to a wide variation 

 in location due to independent shifting of axostyle and nucleus, and 

 to a less extent to the detachment of the blepharoplast from its usual 

 relation to the nucleus. 



14. Plasmotomy is long delayed after nuclear mitosis and during 

 this period many widely varying positions of the two daughter nuclei 

 and their attached extranuclear organelles are rapidly assumed. Some 

 of these may simulate copulation. 



15. The plane of division is longitudinal. Its determination should 

 be based on the fundamental morphological relations of the organelle 

 and not, as by Martin and Robertson, on the chance relations of these 

 structures in the amoeboid postmitotic period. 



16. Multiple fission occurs in the trichomonad flagellates as a 

 normal phase of the life-cycle and results in the formation of an 8- 

 nucleate plasmodium or somatella. We have not been able, as yet, 

 to relate it to a particular stage such as gametogenesis, or to the 

 divisions of a zygote. Three rapidly succeeding synchronous mitoses 

 give rise to 2-4-8-nucleate plasmodia which are not encysted and remain 

 very active throughout the process. The plasmodium disintegrates 

 into its component members by the successive detachment of single 

 merozoites. 



17. The widespread and regular occurrence of the stage of a multi- 

 nucleate Plasmodium among these simple protozoa is significant as 

 an early step in the evolution of the more permanent multinucleate 

 and multicellular aggregates which constitute the Metozoa. 



May 18, 1915. 



Zoological Laboratory, University of California, 

 Berkeley, California. 



