When you press the SEARCH button, the next relatives of the selected species are listed in the Hits-box.
If you check 'Auto search on change' the search will start everytime the currently selected species or any search-relevant parameter changes.
Then number of species listed there is limited by the number given in the 'Results' field. Enter 0 to get unlimited output.
You may also limit the listed relatives by specifying a required minimal score.
When you press the 'Move to hitlist' button, the species list is transferred to the species search result list, where you're able to apply further actions to the found relatives.
Depending on the settings of 'Search/Add/Keep species' in the main query-window the species list is either replaced, added or kept.
Depending on the setting of 'that match/don't match the query' either the list of found relatives is applied or the rest of the species.
When you press the 'Mark hits' button, all species listed in the 'Hits' list will be marked (and all other species will be unmarked).
If you check 'Auto' behind the 'Mark hits' button this will be done automatically after each search.