PLATE 2 



EXPLANATION OF FIGURES 



13 to 1-1 Origin of plastids by cytoplasmic constriction. 



13 Experiment 43, b ; autoplastic culture of the blood from the heart of a 30 mm. 

 embryo. A series of stages showing the formation of a plastid by the constriction 

 off of the cytoplasm of an erythroblast. Examined immediately after the prepara- 

 tion was made. In stage t the surrounding corpuscles are included for comparison ; 

 when the last drawing was made it was supposed that the constriction process had 

 been completed and the plastid entirely detached, but closer observation made 

 evident an almost invisible thread still connecting the two parts, the continuity of 

 which was still further tested by a mechanical disturbance of the cells. It may be 

 noted that there was no cytological difference evident between this newly formed 

 non-nucleated element and the neighboring plastids. Compare the nucleated re- 

 mainder with the erythrocytic nuclei n in figures 10, 11 and 12. 



14 Experiment 49 ; forty-three-hour autoplastic culture from a 27 mm. embryo. 

 Origin of medium-sized plastid from erythroblast by constriction process. 



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