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SCIENCE 



[N. S. Vol. XLI. No. 1051 



ments diminislies. Their tips vacuolize and 

 appear lumpy, giving evidence again of a net- 

 work arrangement of granules. As the con- 

 striction deepens, the cluster assumes the form 

 of an hour-glass. The Janus green stain now 

 disappears at the middle as if the mitochon- 

 drial material were drawn away or had gone 

 into solution. In late telophase the substance 

 of one daughter cell may be torn away from 

 the other cell leaving the mitochondrial fila- 

 ments projecting in naked strands which soon 

 wrinkle and curl and finally coalesce into a 

 lumpy mass. 



Cells in late anaphase and telophase may be 

 caused to assume a spherical shape by mechan- 

 ical agitation or tearing with the needle. The 

 mitochondrial spindle is then very much dis- 

 torted, the filaments become wrinkled and 

 tangled. At the end of the cell division, each 

 daughter cell contains a cluster of mitochon- 

 drial filaments which have already begun to 

 be transformed into a granular network mass 

 which gradually spreads around the nucleus. 

 The mitochondria are not stable structures. 

 Granules at one moment may draw out into 

 threads, or coalesce with their neighbors, or 

 go into solution, freshly formed granules re- 

 placing them. 



In the spermatid the mitochondria mass at 

 one side of the nucleus to form the ISTebenkern. 

 The mitochondrial granules, at first loosely 

 distributed, soon collect into a compact body 

 which stains a solid blue with Janus green. 

 On dissecting the Nebenkern out of the cell, 

 it disintegrates into granules which persist 

 as such for some time. 



The development of the axial filament was 

 closely followed in the cockroach. It origi- 

 nates in connection with an apparent slough- 

 ing ofl: of material from the surface of the 

 Nebenkern. The coiled filament thus formed 

 is bordered on two sides with a longitudinal 

 row of granules collected at very regular in- 

 tervals in small imiform clumps. The fila- 

 ment itself does not stain with Janus green, 

 the bordering granules, however, become in- 

 tensely blue. One may watch the filament 

 gradually uncoil and loosen from the Neben- 

 kern. One end is inserted in a conical knob. 



(the blepharoblast), on the surface of the cell 

 nucleus. As it uncoils, it forms a loop curv- 

 ing along the periphery of the cell. The un- 

 coiling is accompanied by an oscillatory 

 movement which begins at the knob and 

 passes in a wave along the filament. This 

 movement gains in strength until the whole 

 body of the cell is thrown into ever recurring 

 wavps. The movement is instantly arrested 

 when the cytoplasm is torn by the needle. 

 The cytoplasm then goes into solution and the 

 filament either straightens out or deepens its 

 curve possibly according to the character of 

 the wave at the moment the spermatid is torn. 

 The filament remains attached to the nucleus 

 and may be dragged about with a needle. It 

 is elastic and rigid and keeps its shape per- 

 fectly for the short time before it goes into 

 solution. During the process of its elonga- 

 tion the spermatid is very susceptible to touch. 

 A slight prick with the needle will cause it to 

 assume a spherical shape. This is accom- 

 panied by a distortion of the double row of 

 granules alongside the axial filament so that 

 one may observe the wave pass along one row 

 slightly ahead of that along the other. 



When examined in Ringer's fluid or when 

 the spermatid is disturbed by the needle, the 

 clumps tend to round off in the form of ves- 

 icles. This is especially noticeable in the case 

 of the two largest clumps close to the nucleus. 

 Such an appearance is commonly met with in 

 fixed material. As the filament straightens, 

 the cell is drawn out into an attenuated body. 

 The granules along the filament coalesce to 

 form two narrow uniformly homogeneous bands 

 which extend alongside the spherical nucleus 

 to the anterior tip of the spermatid. The 

 nucleus condenses into an optically homo- 

 geneous and highly refractive body which 

 gradually lengthens into the rod shape of the 

 mature spermatozoon. A large double clump 

 of granules which lies immediately behind 

 the nucleus condenses and forms the neck 

 piece. The throwing off of clumps of cyto- 

 plasm was never observed except in prepara- 

 tions in salt solutions or in old body-fluid 

 preparations where such cytolytic action was 

 apparent in all the cells present. 



