Horse outward similarity is an unreliable measure of relatedness. Besides the horse, there are six other species of genus "Equus" in the Equidae family. These are the ass or donkey, "Equus asinus"; the mountain zebra, "Equus zebra"; plains zebra, "Equus quagga"; Grévy's zebra, "Equus grevyi"; the kiang, "Equus kiang"; and the onager, "Equus hemionus". Horses can crossbreed with other members of their genus. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, a hinny, is a cross between a stallion and a jenny (female donkey). Other hybrids include the zorse,
Travels with a Donkey in the Cévennes us the landscape that makes us who we are." Several writers, such as the Scottish novelist Christopher Rush, have written of their own efforts to retrace Stevenson's steps. Accounts include a bicycle trip 25 years after Stevenson's hike and a comic adventure on the part of two British women. A section of Richard Holmes' "Footsteps: Adventures of a Romantic Biographer" chronicles the author's retracing of Stevenson's journey as well. Travels with a Donkey in the Cévennes Travels with a Donkey in the Cévennes (1879) is one of Robert Louis Stevenson's earliest published works and is considered a pioneering classic of