Plate X. Electron micrographs of some sections of sperm 

 tails of invertebrates. 



(a) Transverse section through the tail of a sperm of 

 Psammechimis. Arms can be seen on one subfibril of each 

 doublet, and a more complex bridge is seen at the lower left 

 (betv^een fibrils 5 and 6). Radial spokes can be seen connecting 

 the central fibrils to some of the doublets; note that these 

 spokes run to the subfibril that bears the arms, and that this 

 subfibril appears slightly larger than the other, armless, subfibril. 

 From Afzelius (1959). ' x 220,000. 



{b) Parts of a longitudinal section through the axial fibre 

 bundle of a sperm tail of Ilaematoloechus. At the right the 

 central structure of the bundle can be seen to be connected to 

 the peripheral fibrils lying on either side by a series of spokes. 

 In places a faint dense spiral in the central structure may be 

 associated with the spokes. X 160,000. 



(c) Parts of several transverse sections of sperm tails of 

 Haematoloechus. At the right is an abnormal tail which carries 

 two axial fibril bundles surrounded by an incomplete ring of 

 longitudinal fibrils just inside the cell membrane. The central 

 structure of the axial bundle is seen to be composed of a central 

 dense region surrounded by first a less dense zone and then 

 another dense zone. Prominent radial spokes connect this outer 

 dense zone to the armed subfibrils of the peripheral doublets. 

 The armed subfibrils appear to be solid. >: 200,000. 



{b) and (c) are from Shapiro, Hershenov and Tulloch (1961). 



