THE AXONEME OF THE SPIDER SPERMATOZOON

The axoneme of the spider spermatozoon (Pholcus sp.) has been examined after fixation with a fixative that permits the visualization of the individual protofilaments. The axoneme was found to consist of nine mi crotubular doublers in a circle around three microtubular singlets, th us a 9 + 3 pattern. Each of the three central microtubules contains 13 protofilaments and is flanked by two short filaments, maybe the equiv alent of the central sheath. Distally the central microtubules are sli ghtly flattened. The nine doublers have inner and outer dynein arms an d have the same anatomy as have the doublers in regular 9 + 2 axonemes . Whereas the nine doublers in 9 + 2 flagella have unequal positions i n relation to the central microtubules and hence unequal tasks in flag ellation, the same is nor true for the spider sperm axoneme.