Vol. XII. April, 1907. i\ 7 o. 5. 



BIOLOGICAL BULLETIN 



NOTE ON THE CHROMOSOME-GROUPS OF META- 

 PODIUS AND BANASA. 1 



EDMUND B. WILSON. 



I am led to publish the following preliminary note lest con- 

 fusion should arise from the peculiar relations of the chromosomes 

 in Banasa calva described in the second of my " Studies on 

 Chromosomes," 2 which have now, I believe, become explicable 

 as a result of additional studies on Banasa, but more especially 

 on the genus Metapodins. At the time these relations were de- 

 scribed in Banasa calva they appeared to be unique in that both an 

 unpaired chromosome (apparently an " accessory" chromosome) 

 and a typical pair of unequal idiochromosomes are present in the 

 same species, and four classes of spermatozoa are accordingly 

 formed. The coexistence of these two forms of chromosomes in the 

 same individual has already been considered by more than one 

 writer as a serious difficulty in the way of my general interpretation 

 of the significance of these chromosomes in sex-production. It was 

 (and is) my view that the " accessory " chromosome is the homo- 

 logue of the large idiochromosome and like the latter is distinctive 

 of the female-producing spermatozoa. It seemed, no doubt, an 

 obstacle to this view that an unpaired or heterotropic chromo- 

 some should coexist with a pair of idiochromosomes in the same 

 species, and that it should in one class of spermatozoa be asso- 

 ciated with a large idiochromosome, in another class with a small 

 one. With the material at my command (which included only 

 two testes from the Paulmier collection) I was not in a position to 



'The material on which the observations were made is part of a series procured in 

 the course of an extended collecting trip to the south and west in the summer of 1906, 

 the cost of which was in part defrayed by a grant from the Carnegie Institution of 

 Washington. The results will be published in a more extended form hereafter. 



2 Journ. Exp. Zool. II., 4, 1905. 



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