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A variable kinked-tail mutant was found in 1974 in a moderately inbred stock of mice at Iowa State University, Ames. It was named meander tail and was shown to be completely recessive. Study 8 alizarin-stained skeletons showed all degrees of ankylosis or fusions of tail vertebrae and occasionally other vertebrae. Extreme examples had great reduction in number of tail vertebrae. Affected mice over 2 weeks old commonly also show some unsteadiness, presumably a pleiotropic effect of the mutant. Less commonly, one or both hind legs showed some paralysis. Linkage tests of the mutant, symbolized mea, place it fairly close to brown, b, in chromosome 4, and apparently in the small segment between Ps and Pt.

A semisterile F1 male mouse from an X-ray experiment produced about 25 percent lethal gnome young in outcrosses. These animals were about half normal size, with short tail and small eyes, and died at birth. Surviving progeny were of four classes: 1) like the sire, 2) semisterile, 3) normal, and 4) gnome-producing, but not semisterile. Two independent reciprocal translocations have been identified from the original male, one of the classic type giving semisterile heterozygotes and involving chromosomes 5 and 15. The second translocation seems to be very small, giving the gnome type as one duplication-deficiency product, and the other unbalanced type seeming to pass for normal, although large body size and occasional agnathism may be produced. The small translocation has been found linked with the loci of v (waltzing) and Sl (steel) on chromosome 10. Cytological study has not revealed obvious structural changes. The translocation is now maintained in the homozygous state. The designation T(10;?)2Ho is proposed.

The hypothesis of bipaternity--incorporation of tissue derived from supernumerary sperms into an embryo--to explain the origin of sectorial mosaicism in pigeons was advanced in 1949. Since then, 182 additional examples have come to my attention. Only one was reported to be a gynandromorph; sex ratios generally have been near 1 : 1. No environmental variable has shown significant relation to the origin of the mosaics, and only a slight familial tendency has been indicated. At least 15 color and pattern mutants have been involved, usually contrasting only two alleles. The frequency and its use in crosses. Complex mosaics, involving two or more loci in the contrasts numbered at least 38 cases, of which 11 are examined in more detail, and 6 shown in photographs. Several instances of germinal as well as somatic mosaicism were demonstrated by progeny tests. The bipaternity hypothesis has not been ruled out by evidence in any case.

A mutant characterized by small size, short snout, short middle and inner metatarsals and hallux, low vigor, and poor reproduction appeared in F2 from a cross of BALB/c in 1965. It proved recessive and was named dumpy, with symbol dpy. After some 10 years of maintenance, the stock showed much improved vigor and reproduction, but it is not carried on a pure-strain background. Linkage was found with satin (sa) in linkage group XIV, chromosome 13. Data from female heterozygotes gave about 16 percent crossing over, and from males about 10 percent. Three-point tests involving XtJ showed the map order XtJ-sa-dpy, again with sex difference in crossing over, confirming results of studies by others for this region of chromosome 13.

Textbook presentations of the genetics of coat color in cats are compared with research literature on cat genetics. There is general failure of the textbook authors to identify mutants by contrast with wild-type standard, thus leading to the erroneous conclusion that black is sex-linked and allelic with yellow.

Auto-sexing is shown to be possible with two dominant color factors in the domestic pigeon. These are “almond” and “faded.” The latter appears to have the greater utility as sex distinction can be made at hatching on the basis of down length and beak color, and vigor is normal. The adult homozygous “faded” male is described.

A variable syndrome including polydactyly of feet and wings, shortened legs, undershot beak, short nestling down, and defective plumage was found in a family of Silver King pigeons. Of 25 specimens, none survived to maturity. Breeding data show that a simple recessive pleiotropic factor is responsible, which is symbolized py. A somewhat similar condition was also found in an unrelated family, and appears to be similar in inheritance but not allelic with the previous type.