Horse breed been produced. Such restrictions have led to legal challenges in the United States, sometime based on state law and sometimes based on antitrust laws. Horses can crossbreed with other equine species to produce hybrids. These hybrid types are not breeds, but they resemble breeds in that crosses between certain horse breeds and other equine species produce characteristic offspring. The most common hybrid is the mule, a cross between a "jack" (male donkey) and a mare. A related hybrid, the hinny, is a cross between a stallion and a jenny (female donkey). Most other hybrids involve the zebra (see Zebroid). With
Male/Female (Borofsky) as the centerpiece of a re-designed plaza in front of Penn Station. The project celebrated the Municipal Art Society's centennial and was completed in 2004. The sculpture was given to the City as a gift. "Male/Female" has generated considerable controversy ever since its installation. Its defenders cite the contemporary imagery and artistic expression as complementing an urban landscape, while opponents criticize what they decry as a clash with Penn Station's Beaux-Arts architecture, detracting from its classic lines. It has been named both Baltimore's kinkiest piece of public art, "The Invasion of the 50-Foot She-Male" that "bends genders and may very