THE MITOCHONDRIA AND OTHER STRUCTURES. Ill 



in cases where some abnormal factor caused the cytoplasm along 

 the tail of the spermatozoon to become clumped into nodes, and, 

 in this case, one or more neutral red granules were present in 

 each node (Fig. 49). In the young spermatid the mitochondria 

 are in the form of the granular nebenkern (Fig. 38), which later 

 becomes a clear, homogeneous, spherical body close to the nucleus. 

 No trace of granules can be seen either in the unstained cell or 

 in those stained with Janus green. Within a short period of time 

 (}/2 hour) certain delicate threads appear within the clear 

 nebenkern (Figs. 39 and 40). These threads maybe concentric 

 or otherwise coiled and may represent either the rows of granules 

 under pressure, or they may be the edges of the membrane, which 

 separates the nebenkern into two half spheres, seen at different 

 levels, for very shortly after the threads appear, the nebenkern 

 slides apart into two half spheres and at once becomes granular 

 again (Figs. 41, 42, 43). 



The behavior of the centrosome and the formation of the axial 

 filament, which has been described from fixed material, was seen 

 only in one case, and in that case it was not possible to ascertain 

 just what connection there is between the division of the neben- 

 kern and the formation of the axial filament. The centrosome 

 was seen as a clear paired body near the nucleus, but at a distance 

 from the mitochondrial body (Fig. 38). Later the centrosome 

 occupies a position at the posterior pole of the nucleus near the 

 Nebenkern. After the division of the Nebenkern it was seen as a 

 small opaque body close to the nucleus (Fig. 44). The body is 

 double and, although small, it increases in size with the growth 

 of the tail and later becomes the middle piece (Figs. 46, 49, 50 

 and 51). From this body the axial filament probably is given 

 off and later grows out into an extension of the cytoplasm. 



The mitochondrial bodies, or the two half spheres of the ne- 

 benkern, now elongate as granular sacs (Figs. 45 and 46). The 

 wider end is towards the nucleus and the sacs gradually taper off 

 until they become only a few granules at the other end (Fig. 46). 

 As the tail grows out these bodies grow out one on each side of 

 the axial filament. The sacs do not increase in size, but simply 

 spread out along the axial filament and become crowded into the 

 narrow layer of cytoplasm along the tail, so that as the tail 



