| 100% | ORIGIN | 6 | Charles Darwin's On the __ of Species |
| 73% | EVOLUTION | 9 | Theory in Darwin's On the Origin of Species |
| 73% | ORIGIN | 6 | Darwin's "On the ___ of Species" |
| 64% | DARWIN | 6 | Charles __ wrote On the Origin of Species |
| 59% | ORIGIN | 6 | On the __ of Species, book on evolution |
| 58% | DARWIN | 6 | "On the Origin of Species" author Charles |
| 57% | ORIGIN | 6 | "The ___ of Species" (Charles Darwin book) |
| 54% | MIT | 3 | Sch. on the bank of the Charles |
| 54% | BOSTON | 6 | *City on the banks of the Charles |
| 53% | MIT | 3 | Sch. on the bank of the Charles River |
| 52% | DARWIN | 6 | Author of On The Origin of Species |
| 50% | TIP | 3 | "It's on the ___ of my tongue" |
| 49% | BUKOWSKI | 8 | Charles —, author of the novels Ham on Rye and Post Office |
| 49% | HMSBEAGLE | 9 | Name of the ship that Darwin famously went on |
| 49% | IRAN | 4 | It's on the Gulf of Oman |
| 49% | AGOG | 4 | On the edge of one's seat |
| 49% | HOUSE | 5 | "It's on the ___" (free of charge) |
| 49% | RIVETED | 7 | On the edge of one's seat |
| 49% | ENPOINTE | 8 | On the tips of one's toes |
| 48% | IVES | 4 | Charles —, composer of the works Robert Browning Overture and Variations on America |
| 48% | ENATE | 5 | On the mother's side of the family |
| 48% | EAR | 3 | It's on the side of the head |
| 48% | CEDAR | 5 | Tree that's on the flag of Lebanon |
| 48% | IGLOO | 5 | It's on the Nunavut coat of arms |
| 48% | TASTEBUD | 8 | It’s on the tip of your tongue? |
| 48% | SALIVA | 6 | It's on the tip of your tongue |
| 48% | PAPILLA | 7 | It's on the tip of your tongue |
| 48% | TWEEN | 5 | Kid who's on the verge of adolescence |
| 48% | BEAGLE | 6 | Ship on which Darwin collected material for "On the Origin of Species" |
| 48% | RAY | 3 | 2004 musical starring Jamie Foxx that is based on the life of soul musician Charles |