Studies on chromosomes. II. The paired microchromosomes, idiochromosomes and heterotropic chromosomes in hemiptera

I n investigating the physiological significance of the chromosomes and their individual values in heredity, it is important to determine as accurately as possible how far they are differentiated in respect to individual behavior, and to ascertain by the comparative study of different forms to what extent the chromosomes can be grouped in well-defined classes.T h e work of Henking, Paulmier, Montgomery, Gross and Stevens on the Hemiptera has shown that this group is peculiarly favorable for such a study; and I believe from my own observation that no group of animals has thus far been examined that offers greater advantages in this direction.'But although the general results obtained by the above-mentioned observers are of great value and interest they nevertheless show many discordances of detail that stand in the way of a consistent general interpretation of the phenomena, while some of Gross's conclusions are a stumbling block in the way of the whole theory of the individuality of the chromosomes.For this reason I propose in this paper to record a series of observations that I hope may serve to clear away some of the confusion that now exists in the accounts of the subject, and that open the way, I believe, to a true interpretation of the "accessory chromosome" and its relation to the determination of sex.In a series of suggestive papers ('01, '04, '05) Montgomery 'Attention is called to the Appendix in which are briefly recorded facts, determined by later observations, that exactly realize the theoretic expectation regarding the sexual differences of the chromosome-groups, stated at p. 539.An abstract of these observations was published in the issue of Science for Oct. 20, 1905.'1 am much indebted to Mr. Uhler's kindness in identifying many of the species examined.'I have in the previous paper acknowledged my indebtedness to Dr. Paulmier's generosity in placing He has since added to this at my disposal his entire series of preparations of Anasa and other insects.indebtedness by sending me from time to time a large amount of valuable living material.'Cf.Montgomery, '01, Figs.96-98.*Montgomery's study of the facts in Euschistus ('98) is not in point, since he was here undoubtedly dealing with the idiochromosomes and not with the m-chromosomes.