414 E. L. SHAFFER. 



are derived from the nucleus. It is thus evident that the facts 

 are conflicting on all sides. If it is true, as I have previously 

 stated (p. 408), that the mitochondria are not present in the 

 primary spermatogonia of Passalns, then we cannot maintain 

 that they are persistent and self-perpetuating. I am, however, 

 not entirely convinced that they are absent in the primary 

 spermatogonia and shall await fresh material for a study of the 

 living cells. 



It is possible that the increase in number of the mitochondria 

 during the growth period is due to a simple growth and division 

 of those already present. I cannot find any evidence for this 

 in my material. In nearly all the growth stages of the first 

 spermatocytes, there is present a denser and more deeply stain- 

 ing perinuclear zone. Schafer (1907) has figured similar con- 

 ditions in Dytiscus, while Voivnov (1903) shows it more strikingly 

 in Cybister and calls it the "zona interna." During the matura- 

 tion divisions, the "zona interna" surrounds the spindle peri- 

 pherally and forms the Nebenkern of the spermatid. As Dues- 

 berg (1910) has pointed out, it is quite evident from this be- 

 havior that the "zona interna" is really of a mitochondrial 

 nature. Giardina (1904) has studied the oocytes of a number 

 of forms (Periplaneta, Stenobothrus, Gryllus, Mantis, etc.) and 

 figures well-defined perinuclear zones usually of a granular na- 

 ture. Whether this zone is formed by a diffusion of chromatin 

 in the form of a solution out of the nucleus into the surrounding 

 cytoplasm or whether it arises in situ in the cytoplasm by inter- 

 action with the nucleus, is a question which Giardina discusses 

 at considerable length. He concludes in favor of the latter view. 

 Payne (1917) has described a similar perinuclear zone in the 

 oocytes of Gryllotalpa, but he definitely states that this consists 

 of mitochondria. As the oocyte grows, the mitochondria 

 migrate centrifugally into the cytoplasm. Vejdovsky (1911-12) 

 shows the mitochondria arranged in a definite perinuclear zone 

 in the spermatocytes of Diestramena. It thus seems quite prob- 

 able that the perinuclear zones described by Giardina are really 

 of a mitochondrial nature. The occurrence of this zone in such 

 close connection with the nucleus and especially during a period 

 when the mitochondria are certainly increasing in number, is 



