50Among the small laboratory animals the most commonly used species for studies on egg transfer have been the mouse, rat, and rabbit. Other small animals in which egg transfer has been performed, though only to a limited extent, include four carnivores — the cat (Felis catus), the dog (Canis familiaris), the ferret (Mustela putorius furo), and the mink (Mustela vison) — and two rodents — the golden hamster (Meso-cricetus auratus) and the Mongolian gerbil (Meriones unguiculatus). Observations on these six species will be presented in this chapter, which will also include transfer between species and to ectopic sites.