96 CYTOPLASMIC STRUCTURES [CH. 



and chromosomes, the mitochondria have such appearance 

 as is described and figured by MEVES (1900, 1907), MONT- 

 GOMERY (1911 #), and othefs. More recently, however, 

 GATE N BY (1917, 1918) has re-investigated the subject in 

 Moths and Molluscs and concludes that the appearances 

 commonly seen are deceptive in consequence of faulty 

 fixation. He finds that fixatives containing acid or alcohol 

 either destroy the mitochondria or distort them so badly as 

 to make accurate observation impossible. He maintains 

 that the long strands frequently seen, especially in dividing 

 cells, have in most cases no real existence, but are produced 

 by the running together of bodies which are in life semifluid 

 vesicles 1 . Some of his figures, taken from Moths, are repro- 

 duced in PL XI. According to GATENBY the mitochondria 

 appear in Lepidoptera as a cloud of granules partially en- 

 circling the nucleus of the spermatogonium and early sper- 

 matocyte. During the growth-phase the granules become 

 hollow and filled with a non-staining substance; the vesicles 

 so formed enlarge and show a tendency to, coalesce, but the 

 coalescence at this stage maybe due to the action of the fixa- 

 tive. During the spermatocyte divisions the mitochondrial 

 vesicles become separated, apparently passively, into the 

 daughter cells ; they may be drawn out along the length of 

 the spindle and coalesce to elongated strands, which then 

 break apart, but there is no regular division of the individual 

 vesicles, nor is it clear that their separation into the daughter 

 cells is at all closely controlled by the spindle mechanism. 

 In the spermatid the mitochondria take on a new phase. 

 The vesicles begin to flow together and form a tangled 

 filament, derived from the outer staining layer of the 

 vesicles, enclosing in its meshes a non-staining substance 



1 Paludina is an exception ; its spermatocytes have bent, rod-shaped 

 mitochondria. 



