CHAPTER IX 



THE CHROMOSOMES AND MITOCHONDRIA OF 



GERM CELLS 



No account of the germ-cell cycle in animals can be 

 considered complete without at least a brief reference 

 to the history of the chromosomes and mitochondria 

 of germ cells. The chromosomes have for many 

 years been recognized as the most important visible 

 bodies in the cell, and their behavior during the germ- 

 cell cycle has convinced most zoologists that they 

 may also be regarded as the bearers of hereditary 

 factors. The mitochondria, on the other hand, 

 are cellular constituents which have only compara- 

 tively recently come into prominence in cytological 

 literature, and ideas concerning their nature and 

 functions are still in a very chaotic condition. 



The Chromosome Cycle in Animals 



A few general statements regarding the behavior of 

 the chromosomes during cell division, maturation, 

 and fertilization are contained in Chapters I nnd II. 

 We may recognize a rather definite chromosome cyc-le 

 as a part of the germ-cell cycle, and it is to certain 

 events in this chromosome cycle that our attention 

 will be directed in the following i)aragraphs. It is 

 best to begin our discussion, as in the gencrnl review 



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