Henley C, Costello D P, Thomas M B, Newton W D
Proc Natl Acad Sci U S A. 1969 Nov;64(3):849-56. doi: 10.1073/pnas.64.3.849.
The living spermatozoa of the flatworm Mesostoma georgianum have a sperm body about 100 mu long and 0.5 mu wide, and two motile free flagella, ca. 200 mu long. In sections examined with the electron microscope, these flagella have the usual nine pairs of peripheral doublet microtubules and have a single central core unit which is connected to the A members of the doublets by spokelike structures. There are also short connections between the doublets and the flagellar membrane. In material negatively stained with phosphotungstic acid, the doublet microtubules seem to have very different elastic properties than the core; they tend to fall on the copper grids in coils of rather uniform diameter (2-4 mu), while the core is much more rigid and is often found extending alone, along a relatively straight course, for very long distances (up to 73 mu). After negative staining, the core has a striking appearance with a dense center around which are wound two hollow structures in a double helix of 45 degrees pitch. The center-to-center distance of each gyre is approximately 650 A, and the hollow structures are ca. 180 A in diameter.
格鲁吉亚中口涡虫的活精子有一个约100微米长、0.5微米宽的精子体，以及两条可游动的游离鞭毛，约200微米长。在用电子显微镜检查的切片中，这些鞭毛有通常的九对外周双联体微管，并有一个单一的中央核心单元，该单元通过辐状结构与双联体的A微管相连。双联体与鞭毛膜之间也有短连接。在用磷钨酸负染色的材料中，双联体微管的弹性特性似乎与核心有很大不同；它们往往以直径相当均匀（2 - 4微米）的螺旋状落在铜网上，而核心则更坚硬，经常被发现单独沿着相对直的路径延伸很长距离（长达73微米）。负染色后，核心呈现出一种惊人的外观，有一个致密的中心，围绕该中心缠绕着两个中空结构，呈45度螺距的双螺旋。每个螺旋圈的中心距约为650埃，中空结构的直径约为180埃。
