428 ELMER L. SHAFFER. 



genesis. Not only do they have a characteristic behavior which 

 seems to be quite general in the insects, but they are present 

 in all generations of the male germ cells. There are many dis- 

 crepancies in the literature on this point, some workers maintain- 

 ing that the mitochondria disappear at various times. Buchner 

 ('09) has described a disappearance of the mitochondria during 

 mitotic division in the spermatogonia of Gryllolalpa, but on the 

 contrary Duesberg ('10), working on the same form, has shown 

 that the mitochondria do not disappear at that time. Wilke 

 ('13) states that in Hydrometra the mitochondria are absent from 

 some of the spermatogonia and in some cases from the spermato- 

 cytes. I am inclined to believe that the disappearances of 

 mitochondrial structures is in all cases due to improperly fixed 

 material. In fact, there is some evidence from Wilke's figures 

 that this is the case. In the spermatocytes of Hydrometra, 

 Wilke describes a deeply staining perinuclear zone of the cyto- 

 plasm in which are located "yolk-spherules" (Dotterkugeln). 

 These spherules at first homogeneous, begin to show the appear- 

 ance of threads within them and finally definite mitochondria 

 are set free in the cytoplasm, being formed out of the substance 

 of the "Dotterkugeln." His results, however, do not indicate 

 that a reversal of this process might not be taking place. I have 

 often seen in material which has been improperly fixed bodies 

 resembling Wilke's "Dotterkugeln," which are produced by an 

 artificial agglutination of the mitochondria. As I shall later 

 attempt to show, certain methods of fixation may produce a 

 variety of changes in mitochondrial structures ranging from a 

 slight distortion of their form to their complete disappearance. 

 I merely wish to urge the fact here that mitochondria are constant 

 cytoplasmic structures of the cell and when proper technical 

 methods are employed, they can be demonstrated at all periods 

 in the cell-cycle. 



The role of the mitochondria in spermatogenesis is difficult 

 to interpret on the basis of their morphological behavior. The 

 formation of the compact Nebenkern from the filar mitochondria 

 may be an indication of some chemical change in the mitochondria 

 or it may be merely an expression of the compactness which the 

 other cell elements, notably the nucleus, show in the transforma- 



