This is a cross section through a mature sperm cell, or spermatozoon, from C. elegans. At the right is the pseudopod, which the cell uses to crawl. Notice that the pseudopods regular, granular appearance. There are no organelles in the pseudopod; it is filled almost exclusively of a dense fiber network composed of the Major Sperm Protein (MSP). In a crawling cell, this network is in a constant state of assembly, dissassembly, and movement (called "treadmilling"), and is responsible for the motility of the cell. At the left is the cell body, which contains the nucleus (dark spot at the center), mitochondria, and unusual organelles called membranous organelles. To examine the surface features of a sperm, you can look at a scanning electron micrograph.