ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 39 



contains different self-linked genes from those borne by the X chromo- 

 some derived from the mother. 



A logical consequence of the proof that the gynandromorphs arise 

 through elimination is that they should all start as females, i.e. as XX 

 individuals. A second logical consequence is that, starting as an XX 

 individual, the male parts will be XO, and not XY as in the normal 

 male. A striking fact in regard to these gynandromorphs is that the 

 male and female parts and their sex-linked characters are strictly self- 

 determining, each developing according to its own constitution. No 

 matter how large or how small the region is, it is not interfered with by 

 the aspirations of its neighbours, nor is it over-ruled by the action of 

 the gonad. 



In 88,000 flies there were found 40 gynandromorphs, or 1 to 2,200. 

 The fact that most of the mosaics include large regions of the body may 

 mean that elimination takes place more often during the first or second 

 division of the segmentation nucleus, but it may also mean that when 

 smaller regions are involved the gynandromorph would be more often 

 overlooked. Both gonads of the same individual are always alike — i.e. 

 both are testes or both are ovaries — even when the external markings of 

 the abdomen are male on one side, female on the other. This finds its 

 explanation in the assumption that the germ-plasm of DrosophiJa, as in 

 some other flies, arises from a single cell. This cell, arising after 

 elimination, must be either a spermatogonium or an oogonium. Court- 

 ship has been watched in a number of flies that were partly male and 

 partly female. Many of them are indifferent ; some react as males, 

 others as females. 



The only other theory besides elimination that the authors have 

 found it necessary to employ in accounting for the gynandromorphs of 

 DrosophiJa, where the genetic evidence makes the analysis possible, is 

 the theory of Ijinucleated eggs. This applies to two gynandromorp]/ 

 silkworms described by Toyama. Gynandromorphs in birds and 

 mammals are discussed, along with a number of peculiar conditions. 

 That genetic factors determine the sex-condition in certain types does 

 not in itself prove that there may not be influential environmental or 

 nurtural factors in other types. J. A. T. 



The Second-Chromosome G-roup of Mutant Characters in Droso- 

 phila melanogaster. — C. B. Beidges and T. H. Mokcian (Publication 

 278, Carnegie Inst. Washington, 1919, 128-304, 7 pis., 17 figs.). This 

 paper deals with thirty-nine mutant races whose genes lie in the " second 

 chromosome " (arbitrarily defined as that which carries the gene for 

 black and other related genes). The point of the investigation is 

 mapping out of the loci of the various genes in the chromosome in 

 question — a remarkable triumph of experimental analysis. Thus, " star 

 eye " has its gene at the extreme "left" of the chroriiosome, "purple 

 eye " has its gene at the centre near that of black, the " speck " character 

 has its gene near the right end, and "curved " has its position at the 

 right of the central group. Apart from the localization of yenes, the 

 authors discuss the " modifiers " of characters, autosomal and balanced 

 lethals, and the variations in the amount of crossing-over due to specific 

 genes and to such factors as age and temperature. J. A. T. 



