With the introduction of sex hormones some of the early conclusions of geneticists must be discarded. As already pointed out, many characters in females, had they no female hormone to repress them, would show up as male. Sword tail is a good example. One investigator tells us the character is absolutely Y-linked (sex-inked and located on the Y-chromosome). Now we know this is not necessarily so. To read this early work, one might conclude that only one pair of chromosomes was of much consequence in guppies the X and Y-but there are 22 other pairs to reckon with. The early work mentions only yellow, red and black, and occasional blue spots on the body, as if there were no other guppy colors. Yet we know that even on gold males, it is common to see brilliant green patches. Blue-tailed guppies are a favorite color type among fanciers. Some of our loveliest guppies are of this variety. A great deal remains to be learned. Perhaps you will be one to add materially to our knowledge about the fish's inheritance.