SPERMATOGENESIS OF PASSALUS CORNUTUS. 4! I 



lie with their length extended in the direction of the main axis 

 of the cell. Sections of the cell taken at right angles to its longi- 

 tudinal axis show the mitochondria on end view (Fig. 25^). 

 As the nuclear membrane dissolves and the first maturation 

 spindle is forming (Figs. 10, 29), the mitochondria are usually 

 localized at one side of the spindle. When the spindle has fully 

 formed, the mitochondria begin to envelop it at first from one 

 side (Fig. u) and later entirely surround the outer spindle 

 fibers, being equally distributed along their lengths (Figs. 13, 

 30, 31). By the time the metaphase has been reached, the 

 spindle has been entirely surrounded by mitochondria. Figures 

 12, 32, 33, 34 represent cross-sections at different levels of the 

 first maturation spindle at metaphase, showing clearly the rela- 

 tions of spindle and mitochondria. As is best seen in the ana- 

 phase (Figs. 13, 35) they do not entirely reach to the two poles 

 of the spindle, so that there is a short uncovered part near the 

 centrosomes. 



The question arises as to the method of movement of the 

 mitochondria in order that they establish this relation with 

 the spindle; is it an active or a passive movement? Many 

 observers on living cells have noted that the mitochondria 

 are generally of a vibratile or motile nature. According to 

 Lewis and Lewis (1914) the mitochondria are never at rest; 

 "a single mitochondrium sometimes twists and turns rapidly as 

 though attached at one end, like the lashing of a flagellum, then 

 suddenly moves off to another position in the cytoplasm as though 

 some tension had been released" (p. 332). If it is true that they 

 possess the power of active movement, it may be possible in 

 this way to explain their movement to the spindle. Lewis and 

 Robertson (1916) state that "the mitochondria migrate from the 

 two masses of mitochondrial granules and elongate towards the 

 poles of the spindle," etc. (p. 108). Whether they mean by this 

 an active or a passive migration is not clear from their account. 

 It seems highly improbable that the movement is active. Some 

 observers have supposed that their movement is influenced by 

 the centrosomes, but there is no conclusive evidence that this 

 is the case. It is more likely that the movement of the mito- 

 chondria to their position on the spindle is due to the cytoplasmic 



