larly in division, has never been solved satisfactorily. One view is that 

 they arise de novo; another that they replicate by some form of fission. 

 Certainly the number does increase or decrease in specialized cells and, 

 as a general rule, it must be assumed that replication occurs at cell divi- 







^ 



3# 





Figure 3-12, Electron Micrograph of Grasshopper Testis Cell in Telo- 

 phase of Meiosis. The elongated mitochondria are shown being pinched in 

 half at the constricting cleavage furrow, with the result that they are dis- 

 tributed in approximately equal numbers to each daughter cell. Approxi- 

 mately 5000X. (From Tahmisian, T. N., Powers, E. L., and Devine, R. L., 

 1956. "Light and Electron Microscope Studies of Morphological Changes 

 of Mitochondria During Spermatogenesis in the Grasshopper," /. Biophys. 

 Biochem. Cytol, SiippL, 2, Fig. 23, Plate 105. Courtesy of Dr. T. N. Tah- 

 misian, Argonne National Laboratory.) 



sion since each daughter cell receives roughly half the number of mito- 

 chondria present in the mother cell (Figure 3-12). 



Accumulated facts concerning both the structure and function of the 

 mitochondrion serve to illustrate the complexity of metabolic interaction 

 which may be associated with any particular subcellular organelle. 



STRUCTURE AND FUNCTION OF CYTOPLASMIC ORGANELLES / 37 



