Mutant Dalek embryo

The Mutant Dalek Embryos were failed attempts at creating new Daleks on 1930s Earth. The creatures vaguely resembled Kaled mutants, though the lack of eye and tentacles gave them a more brain-like appearance. Being the last Daleks in existence, the Cult of Skaro had to act quickly in order to ensure their race's survival. Trying to grow new Dalek embryos failed to create anything, as the flesh was too weak.

The Cult moved on to converting Humans into Human-Daleks in the Final Experiment and the embryos were dumped in the sewers to die in the dark. This is where the Doctor found one, which alerted him to the Daleks in Manhattan. (DW: Daleks in Manhattan)