308 FERNANDUS PAYNE 



is a centro sphere, and perhaps the mitochondria multiply at its 

 expense, but I have no evidence that such is the case. In fact, 

 I am not inclined to the belief that the centroplasm or sphere 

 ever gives rise to mitochondria. They have been figured as 

 lying around the sphere, but this is no proof that they arise from 

 it. In Gryllotalpa there is no indication that a sphere or the 

 spindle and astral fibers persist after cell division. 



Certainly there is no indication that the mitochondria arise 

 from the nucleus. They persist throughout the entire growth 

 period. In the first part they are granular, but later become 

 arranged in elongated filaments. The filaments remain in a 

 mass, however, until the prophase of the first spermatocyte divi- 

 sion. In metaphase they are found on the outside of the spindle, 

 with their long axis in the direction of the long axis of the spindle 

 (see figures). They remain in this position until the chromo- 

 somes have divided and have moved to the ends of the spindle. 

 The mitochondrial filaments then break in or near the middle, 

 part moving to one pole and part to the other. In the second 

 division they take a similar position and divide in the same 

 way. I have no evidence as to the mechanism of this division. 

 Montgomery ('11) states that the elongated threads do not 

 divide autonomously in Euschistus, but are broken by the con- 

 striction of the cell body. This is not the case in Gryllotalpa, 

 as the division takes place before the constriction of the cell has 

 progressed far enough. Further, this constriction would not 

 explain their movement along the spindle. As a result of the 

 division of the mitochondrial filaments, each spermatid receives 

 a mass of mitochondria and, as is characteristic of the insects, 

 the mass takes part in the formation of the tail of the sper- 

 matozoon. While the identity of the mitochondria as granules 

 or threads is lost in the last stages of the development of the 

 spermatozoon, the earlier stages in this development indicate 

 that they form a sheath for the axial filament. In the fully 

 formed spermatozoon the tail appears as a homogeneous struc- 

 ture. The axis cylinder is not even visible. 



In the female sex cells the mitochondria are present in the 

 earliest stages observed (oogonia) and migrate out into the cyto- 



