MITOCHONDRIA IN PLANT AND ANIMAL CELLS. 215 



growth and maturation of the egg as Van der Stricht ('09, plate i) 

 and his pupils, among others, have abundantly shown. The 

 causes underlying these strange movements of mitochondria are 

 obscure. 



Furthermore, during cell division the mitochondria are dis- 

 tributed in much the same way in plants as in animals. They 

 persist during the whole process; they are absent in the spindle 

 area, whether a definite spindle be formed or not; and they are 

 divided in approximately equal amounts between the two 

 daughter cells. 



22 



FIGS. 22, 23 and 24. Spermatogonium, spermatocyte and spermatid from mouse 

 testis fixed in formalin and bichromate (Regaud IVJ3) and stained with iron hema- 

 toxylin. Note diffuse arrangement of mitochondria, circumnuclear condensation 

 and final diffuse arrangement. (1,500 diameters.) 



In animal cells they are almost invariably disposed in a radial 

 fashion about the centrosome: contrasting strongly with their 

 appearance in Pustularia during spore formation when they 

 are entirely absent from the region near the centrosome and are 

 found in a clump in the portion of the cells farthest away from 

 it (Guilliermond, '136, p. 649). No examples of a radial arrange- 

 ment have to the best of my knowledge been described in the 

 higher plants but this may be due to the well-known absence of 

 a typical centrosome in the Angiosperms. 



It will be noticed that in animal cells rather more variations 

 obtain in the arrangement of mitochondria than in plant cells, 

 but this seems to be correlated in some way with the fact that 

 animal cells are more generally polarized. I mean polarized 

 for irritability, conduction, secretion, contraction and so forth, 

 properties which do not play so great a role in the life of plants, 

 where separate regions of the cell are not so distinctly marked off. 

 Accordingly if one were searching for variations in the distribu- 



