1) A hybrid strain between Chinese and Japanese races of the silkworm was inbred since the summer 1914, and it proved itself to breed true with regard to the larval marking, to the cocoon colour and to many other important characters. The larvae of this strain were of the normal marking of rather intense type, their subdorsal spots were characteristically distinct and well defined. In the summer culture, 1919, I found a single larva with unpaired lunulepattern together with some individuals with unusually small, paired lunules. In the next generation produced from a mating among the individuals furnished with small lunules, only one male caterpillar was found to be "no-lunule" (autumn 1919). We got IIo no-lunule offspring by mating the animal in question to his two sisters. The type had not been known to breeders and scientists up to the date. 2) No-lunule marking is characterized by the presence of the eye-spots and the total absence of lunules and the star-spots, and also of the subdorsal spots (Pl. 4, figs. 8, 9). The eye-spots in a no-luuule larva (Pl. 4, figs. 4-7) are less intense in colour than in its normal brothers and sisters (Pl. 4, figs. 1-3). 3) No-lunule is dominant to the normal marking, it suppresses the development of lunules, stars and subdorsal spots, while it reduces the intensity of eyespots. No visible effect can be seen when the no-lunule gene is present with two doses of the plain gene. 4) Zebra marking i s not affected by no-lunule. The intensity of the multilunar spots is, on the contrary, markedly reduced in the presence of the no-lunule gene. 5) No-lunules were continuously bred inter se, but they have neither bred true, nor increased the percentage of no-lunules, but remained heterozygous indefinitely, segregating no-lunules and normals in a ratio of about 2 : 1. 6) When no-le/wiles were crossed to normals, the result was the p roduction of two phenotypes in a ratio of 1 : 1. 7) The fact that the actual numbers of no-lunules always come short to theoretical expectation, could be accounted for by differential viability during the postembryonal development. The death-rate is higher by some 15 per cent. in no-lunules than in normals. 8) Segregated n o r mals proved themselves homozygous. 9) We will represent no-lunule gene by a symbol NI, and its normal allelomorph by nl. 10) There are met with a considerable number of shrinked eggs in the egg-batch deposited by a no-lunule female mated to a no-lunule male. Although some shrinked eggs may be found in egg-batches produced by normal moths, the percentage of them is decidedly higher in eggs of no-lunules mated inter se, the difference amounting fairly to 25 per cent. The shrinked eggs should have contained duplex no-lunule genes. The number of shrinked eggs in batches deposited by no-lunule females crossed to normal males is only as large as in the normal strains. Thus we may safely conclude that the lethal action of Nl gene is zygotic, but not gametic. The shrinked eggs must be fertilized eggs in which the embryos ceased to develop in an early stage of ontogeny. 11) The genetic behaviour of no-lunule silkworm is very similar to those cases of the yellow mouse (CUENOT, DURHAM, CASTLE and LITTLE, etc.), the black-eyed-white-spotted mouse, Beaded or Diclzaete or Notch Drosophila (MORGAN and others), the red-nerved Oenotlzera (HERIBERT-NILSSON), the yellowish-green-leafed Urtica (CORRENS), the yellowish-leafed Antirrhinum (BAUR), and the red-stemmed-white-flowered Portulaca (ENOMOTO). There had not been any reported case of lethal factor in the silkworm, hitherto.
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