Each cell has four flagella of equal length, in which the flagella are shorter than the length of the cell. The flagella emerge from the apical depression in pairs and point in opposite directions, running parallel to the long side of the cell. Due to their emergence from a deep depression, the mechanical force the flagella can produce is restricted. Other lineages with non-depressed flagellar insertions can produce higher amounts of flagellar force, because the flagellar base is not geometrically limited. The flagella of "Tetraselmis" species are thick, covered in mucilaginous material, and have a blunt end. They are also covered in flagellar hairs which are loosely attached to the cell exterior; they are cross-striated with two scale layers on flagella. See figure 3 for a detailed picture of flagella including their scales and hair. The inner layer is compact and densely covers the flagella, and hair cells are attached to the cell membrane through small sections of membrane that are not covered due to patterning. The outer scale layer is made of small-round scales which are mainly used to overlap bare membrane not covered by the inner scales. The inner scales are larger than the outer scales, and usually resemble a pentagon or square in shape. See figure 1 for a generalized drawing of flagellar scales. The flagellar hairs have a distinct sequence of structural components, the proximal filament connects the flagellum and cell surface, this is followed by the tubular shaft, then the transition zone in which the shaft is modified, followed by a stretch of linear globular subunits, and the hair ends with a distal filament. The distal filament and transition zone are the only components that are not produced by certain species. Flagellar hairs have a fixed number of distal subunit repeats, which varies between 2-44 subunits depending on the species. Thus, flagellar hairs are a good morphological tool for species comparison and classification. Figure 1 includes these hairs on the flagella drawing. Species use their flagella to travel in straight lines while rotating along their axis, in which they travel in one direction for long distances and then abruptly change directions instantaneously without stopping. Some species differ from this pattern of movement and move in less rigid and structured fashion.