Sorry, please simplify your search. This isn't the smartest search engine in the world.
For example . . .
If you were searching for "gastropod eggs" ...
First -- do a QUICK SEARCH (top box) on "gastropod" (without the quotes)
Second -- use the second search box to NARROW the search down to "egg" (without the quotes)
Avoid plurals. For example, seach for shark NOT sharks.
Did you try to go back a page and refine your search? This doesn't always produce the expected results.
Alternatively, start a new search session using one of the Quick Index options shown in the huge menu on the left.