Last month, Pokemon Go released its first major update, unleashing 80 new Pokemon species (first seen in Pokemon Gold and Silver) into the wild for players to escape. Since Pokemon Go doesn't release any "how to" guides or in depth details about the game to players, it fell to the Pokemon Go community to figure out some of the hidden surprises for the game.
One of the weirder discoveries is that many Gen 2 Pokemon do NOT hatch from eggs. Although players initially assumed that Pokemon like Chikorita, Cyndaquil, or Totodile were part of the egg pool, enough time has passed (and enough eggs have been hatched) to determine that 16 Gen 2 Pokemon simply aren't part of the game's egg pool.
According to the Pokemon Go fan community the Silph Road, the missing Pokemon are: Chikorita, Cyndaquil, Totodile, Sentret, Hoothoot, Ledyba, Spinarak, Chinchou, Marill, Hoppip, Sunkern, Murkrow, Snubbull, Teddiursa, and Houndour.
Some of these Pokemon (like Sentret or Ledyba) were probably excluded because they're considered the "common" Pokemon from Gen 2. In November, Pokemon Go pulled common Pokemon like Pidgey, Caterpie, and Weedle from the egg pool in order to keep players interested in the game. So, it makes sense that Pokemon Go would exclude equivalent common Pokemon from the egg pool with the new update.
However, that doesn't explain the absence of Pokemon like Teddiursa, Houndour, or the Johto Starters. Considering that eggs are the only way for many players to obtain Pokemon that aren't commonly found in the area, it's strange that these Pokemon aren't included in the game's egg pool.
We'll have to see if this is just an oversight, or if Pokemon Go has some sort of plans for the missing Pokemon in the future.