Which method is primarily used for the detection of organism motility?

The direct wet examination is the primary method used for the detection of organism motility because it allows for the visualization of live organisms in a fresh sample. By placing a drop of specimen on a microscope slide and covering it with a coverslip, practitioners can observe the natural movements of motile organisms. This method is particularly useful for organisms such as protozoa and certain helminths that exhibit active movement.

In contrast, the other methods listed involve processes that may not effectively preserve the motility of organisms. Knott's concentration, for example, is a technique often utilized for detecting microfilariae in blood samples, but it focuses on concentrating and identifying specific parasites rather than directly observing movement. Baermann's concentration is primarily used for isolating larvae from fecal samples, which also does not allow for direct observation of motility. Lastly, a permanent stained fecal smear involves killing and staining organisms to identify them, which completely eliminates the possibility of observing movement. Thus, the direct wet examination stands out as the most effective technique for assessing motility.