Previously (WBG 7-2:24) I described an 'invisible' (cryptic) allele of tra-2, e1875, which has no obvious phenotype by itself, but fails to complement strong alleles of tra-2. Invisible alleles of tra-1 and tra-3 have now been obtained, which have interesting properties. Strong loss-of-function (lf) alleles of tra-1 cause recessive masculinization of XX animals, while gain-of-function (gf) alleles cause dominant feminization of both XX and XO. The invisible tra-1 allele, e2332, was isolated as a feminizing suppressor of a weak tra-2 mutant, e1209. Suppressors of e1209 were screened for using a strain mab-1(e1228); 09): XX populations of this genotype consist only of small weakly self-fertile intersexes, and revertants with a healthy female or hermaphrodite phenotype are easily detected. By itself, e2332 is almost wild type. In trans with a deficiency, or an lf allele such as e1099, it behaves as a weak lf allele. Animals of genotype e2332/e1099 XX exhibit variable gonad abnormalities, often confined to only one gonad arm. Non-gonadal structures are normal. The modifying mutations mab-1 or mab-11 (which also affect tra-2(e1209) ) alter the phenotype of e2332, enhancing both somatic masculinization and germline feminization, as shown in this table: [See Figure 1] Although e2232 is a spontaneous allele, apparently induced by mut-6, no Tc1 or Tc3 insertions in the tra-1 region have been detected. Alleles with similar properties have also been obtained with EMS, though all of these cause stronger masculinization than e2332. The mab modification seems to convert them into gf alleles that are able to suppress e1209. These observations suggest that the distinction between lf (masculinizing) and gf (feminizing) alleles of tra-1 may not be as tidy as previously appeared. Mutations of tra-3 cause partial masculinization of XX animals. The invisible tra-3 allele was found in a strain carrying lev-11(x21), as a linked mutation e2333. By itself, or in trans with a tra-3 null allele (e1107), it causes no masculinization. However, if an animal, genotype e2333/e1107 XX, is selfed, one quarter of the progeny (the e1107 homozygotes) exhibit a Tra-3 phenotype. In contrast, e1107 progeny of +/e1107 animals are hermaphrodite, only exhibiting a Tra-3 phenotype in the next generation, because of a maternal rescue effect. Thus, e2233 eliminates the maternal rescue, perhaps by reducing the dowry of functional tra-3 product below a critical level. However, a single zygotic dose of e2333 can supply sufficient activity to give a hermaphrodite phenotype.