File:Contributions to the genetics of Drosophila melanogaster (1919) (20501423650).jpg

Title: Contributions to the genetics of Drosophila melanogaster
Identifier: contributionsto00carn (find matches)
Year: 1919 (1910s)
Authors: Carnegie Institution of Washington; Morgan, Thomas Hunt, 1866-1945; Bridges, Calvin B. (Calvin Blackman), 1889-1938; Sturtevant, A. H. (Alfred Henry), 1891-1970
Subjects: Drosophila melanogaster; Heredity; Karyokinesis
Publisher: Washington, Carnegie Institution of Washington
Contributing Library: NCSU Libraries
Digitizing Sponsor: NCSU Libraries

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THE ORIGIN OF GYNANDROMORPHS. 97 characters of the opposite sex. The condition is a very rare one and is usually shown in the external organs only." In the Philosophical Transactions for 1734 is a full account of a bilateral gynandromorph lobster by Dr. F. Nichols. The drawings of the external parts show that the animal is female on the right side and male on the left. Dissection showed an ovary with eggs on the right side, and a testis with vas deferens on the left. This case is exactly like the bilateral gj^nandromorphs of Drosophila, and is the only case known to us of a strictly bilateral type of gynandromorph in the group Crustacea. Olga Kuttner (1909) found a wild individual of Daphnia pulex that had some male characters on one side but had two ovaries. Twelve broods were produced and in nearly every brood some individuals were mixed gynandromorphs, but nearly all were predominantly female. A similar case has been recorded by Banta for Simocephalus vetulus, (1916). In a pedigreed strain there suddenly appeared" a large number of "sex intergrades— males ^vith one or more female secondary sex characters, females with one to several male characters, and some hermaphrodites with vari- ous combinations of male and female secondary sex characters." The more extreme intersex individuals fail to propagate; others, less modi- fied, reproduce. By propagating from female \jX^\l-^!^J:"'^^^^'d r intergrades mixed broods of males, females, and intergrades are obtained. The noteworthy point here is that the intergrades are mosaics rather than blended forms of the two sexes. text-figuhe 69. GYNANDROMORPHS IN MOLLUSCS. The molluscs, like the Crustacea, contain a number of hermaphro- ditic species, but there are also species with separate sexes. Here, too, cytological study has failed as yet to demonstrate sex chromo- somes. One species of Crepidula is male in the juvenile state and female in older individuals, at least when certain external conditions are fulfilled. Gould has recently shown that when young males are placed in the vicinity of large females the males absorb their testes and genitalia (ducts and penis) and develop ovaries and oviducts. This case recalls in many ways the conditions in Bonellia as described by Baltzer. If the embryos of Bonellia are isolated they become sexual females without showing the male stage. If, however, the embryo, when ready to settle down, comes to rest on the proboscis of a female it develops into a rudimentary male. A few embryos in cultures may show intermediate or rather hermaphroditic conditions. The cirri- peds referred to above appear, according to one interpretation, suscep-
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