| 100% | ORIGIN | 6 | Darwin's "On the ___ of Species" |
| 100% | ORIGIN | 6 | Charles Darwin's On the __ of Species |
| 93% | EVOLUTION | 9 | Theory in Darwin's On the Origin of Species |
| 74% | ORIGIN | 6 | On the __ of Species, book on evolution |
| 67% | DARWIN | 6 | Charles __ wrote On the Origin of Species |
| 63% | ORIGIN | 6 | "The ___ of Species" (Charles Darwin book) |
| 63% | TIP | 3 | "It's on the ___ of my tongue" |
| 61% | HMSBEAGLE | 9 | Name of the ship that Darwin famously went on |
| 61% | DARWIN | 6 | Author of On The Origin of Species |
| 61% | IRAN | 4 | It's on the Gulf of Oman |
| 61% | AGOG | 4 | On the edge of one's seat |
| 61% | HOUSE | 5 | "It's on the ___" (free of charge) |
| 61% | RIVETED | 7 | On the edge of one's seat |
| 61% | ENPOINTE | 8 | On the tips of one's toes |
| 60% | ENATE | 5 | On the mother's side of the family |
| 60% | EAR | 3 | It's on the side of the head |
| 60% | BEAGLE | 6 | Ship on which Darwin collected material for "On the Origin of Species" |
| 60% | CEDAR | 5 | Tree that's on the flag of Lebanon |
| 60% | IGLOO | 5 | It's on the Nunavut coat of arms |
| 60% | TASTEBUD | 8 | It’s on the tip of your tongue? |
| 60% | SALIVA | 6 | It's on the tip of your tongue |
| 60% | PAPILLA | 7 | It's on the tip of your tongue |
| 60% | TWEEN | 5 | Kid who's on the verge of adolescence |
| 60% | TEA | 3 | S___k is one of the most expensive items on any restaurant menu |
| 59% | SEAL | 4 | It's on the back of the $1 bill |
| 59% | NAIL | 4 | It's on the tip of one's finger |
| 59% | NRA | 3 | Group that's on the side of gun rights |
| 59% | HARDR | 5 | Rating that's on the cusp of NC-17 |
| 59% | GLUE | 4 | It's on the back of a postage stamp |
| 59% | EVEL | 4 | It's on the Motorcycle Hall of Fame roster |