WHITEHEAD'S claim1 to describe hybrids between Tilapia nigra and T. zillii in two waters in which both species had been introduced could be accepted only if supported by unequivocal evidence. His only evidence that T. zillii was one of the parents of the problematical fishes is that this was the only species other than T. nigra known to be introduced. We know enough of stocking accidents to place no reliance on this, especially when, as in this case, all the evidence points in another direction.