212 



N. H. COWDRY. 



lost; but in the fully mature forms, as they occur in the circula- 

 tion in man, mitochondria are entirely absent. In plants this 

 disappearance is associated with the production of chlorophyll; 

 in animals, with the formation of hemoglobin, two substances 

 with strikingly similar chemical constitution; in both it is 

 progressive and runs parallel with an increase in the degree of 



ffl 



10 



FIGS. 7, 8, 9 and 10. Meristem and parenchyma cells of the bean (after Guil- 

 liermond, '12, plate 18, modified) showing the progressive disappearance of mito- 

 chondria with the formation of plastids containing chlorophyll. 



differentiation and with the age of the cell, general metabolism 

 being diminished and special functions being accentuated (Figs. 



7-15)- 



This diminution of mitochondria in cytomorphosis is really 



of very common occurrence but it attracts attention only in those 



11 12 



FIGS, ii, 12, 13, 14 and 15. Erythroblast, megaloblast, normoblast and ery- 

 throcytes from bone marrow of a rabbit stained vitally with janus green showing 

 the parallelism between the disappearance of mitochondria and the appearance of 

 hemoglobin in the form of a diffuse deposit. (1,500 diameters.) 



cells which normally die and are replaced in large numbers, 

 collectively, in the life of the organism. 



In the separate regions of the cell, also, there is a general 

 similarity in the distribution of mitochondria in plants and 

 animals. \Yhere the cells are elongated, as in the plerome, 



