A solution of picroindigo carmine is used to visualize these cells on a “Christmas tree” stain. Swellings called hydroceles (“hydro-seals”) and hematoceles (“hemato-seals”) can interfere with the storage of these cells, which are found in a pouch of serous membrane called the tunica vaginalis. These cells initiate membrane fusion upon binding to (emphasize) another class of cells’ ZP3 receptors. An influx of calcium ions into these cells through the CatSper channel initiates capacitation. The anterior side of these cells contains an acidic vacuole called the acrosome that secretes (10[1])hydrolytic (10[1])enzymes to break down a different cell’s zona pellucida (“pel-LOO-sid-uh”). These haploid cells develop in the seminiferous tubules and are stored in the epididymis (“epi-DID-uh-miss”) before traveling through the fallopian tubes. For 10 points, name these male gametes that fertilize eggs. ■END■