Version-exclusive Pokemon for Pokemon: Let’s Go, Pikachu! and Pokemon: Let’s Go, Eevee! have been announced.
Both games will feature various Pokemon that can’t be found in the other version, and a handful of those have been announced today. Pokemon: Let’s Go, Pikachu! will feature Oddish, Sandshrew and Growlithe. Likewise, Pokemon: Let’s Go, Eevee! will receive Bellsprout, Meowth and Vulpix.
In order to catch all of the original 151 Pokemon in either game, players must trade between the versions to complete the set – just like in past Pokemon titles. However, if you want to get Mew, you’ll need to purchase a Poke Ball Plus accessory, which comes loaded with the mythical Pokemon.
Source: IGN.com Let's Go Pikachu, Eevee Version-Exclusive Pokemon Announced