166 



F. S. SJOSTRAND AND B. A. AFZELIUS 



Fig. 3. Length-section tiirougii one of the two mitochondria 

 in the middle piece with the mitochondrial membranes as 

 folds from a homogeneous part. Magnification 94,000. 



Fig. 4. Cross-section through the middle piece of the sper- 

 matid showing the characteristic arrangement of the two 

 mitochondria and the tail filaments. Note also the "caudal 

 sheath" like tubiili near the mitochondria. Magnification 

 X 112,000. 



bulges into the mitochondrial half along the central 

 axis. The two central filaments are always in a plane, 

 which would pass between the two mitochondrial 

 filaments. As these latter are known to pass without 

 twisting around each other or around the tail proper 

 (7), it can be concluded that the central filaments also 

 follow a straight course. 



Three equally thick filaments are visible in the 

 light microscope in the grasshopper spermatozoon. 

 Since two are obviously mitochondria, only one of 

 the three is therefore responsible for the flagellar 

 movements. The mitochondria, however, are not 

 complete mitochondria as are those described by 

 Sjostrand (8) and others. As seen in longitudinally 

 sectioned middle pieces each of the two mitochon- 

 drial filaments consists of one part in which the 

 opaque material is homogeneous, and a second part, 

 which shows a regular cross striated appearance. 

 The cross striations are due to a stack of double 

 membranes. These membranes are arranged with 

 very regular spacing and are all of equal size, approxi- 

 mately 230 A thick. The membranes appear as 

 folds of a thin continuous membrane. Alongside 



the mitochondrial threads and within the matrix are 

 tubular formations similar to those of the caudal 

 sheath. 



The high degree of order thus revealed in the 

 grasshopper spermatid makes this material espe- 

 cially suitable for studies in which the ultrastructure 

 as seen in the electron microscope is compared with 

 x-ray analysis. So far, the technical problems en- 

 countered in getting a clean preparation of oriented 

 grasshopper sperm nuclei for x-ray diffraction have 

 not been overcome (10). Birefringence and ultra- 

 violet dichroism measurements performed on living 

 locust spermatozoa, however, have shown that the 

 physical properties of the head closely resemble 

 those of microcrystalline fibers of pure sodium 

 desoxyribonucleate (9). This study also suggests a 

 crystalline or paracrystalline organization of the 

 nucleoproteins within the grasshopper sperm head. 

 It is not known how this organization may be 

 correlated with the idea of the continuity of the 

 chromosomes in the interphase nucleus. Grasse, 

 Carasso and Favard (5, 6) in a study of the spermato- 

 zoon of the edible snail described a similar longitu- 



