146 CHROMOSOMES IN THE SPERMATOGENESIS OF THE HEMIPTERA HETEROPTERA. 



fied chromosomes, of which the most primitive condition would be pairs of hke volume 

 conjugating and dividing in the same way as the autosomes do. One component of 

 each pair must be paternal and one maternal, as I proved some years ago (19016). 

 Therefore, corresponding elements must have become modified in the germ cells of both 

 sexes. A more modified condition would be pairs composed of components of dissim- 

 ilar volume, not conjugating until the second spermatocyte, and dividing in the ma- 

 turation mitoses in reverse order from that of the autosomes. Wilson's observations 

 would indicate that this further specialization has taken place in the spermatogenesis 

 alone, but it is by no means proven that such need to have been the case in all species. 

 Finally, as to the monosoraes, they may be single surviving components of diplosome 

 pairs of which one has been lost in the spermatogenesis as Wilson concludes ; or it is pos- 

 sible that they may have originated by the permanent coalescence of two chromosomes, 

 either autosomes or diplosomes, as I have argued. I wish simply to indicate how di- 

 verse the possibilities are, and to point out that we cannot be sure of these conclusions 

 until more is known of the phenomena in the ovogenesis. 



As to the function of the allosomes, Paulmier (1899) concluded them to be 

 degenerating chromatin masses: "I would make the suggestion . . . that these small 

 chromosomes, or idants (to adopt for the moment Weismann's terminology) contain 

 "ids" which represent somatic characters which belonged t(j the species in former 

 times, but which characters are disappearing." Then I argued (19U16): "The chro- 

 matin nucleoli [allosomes] are in that sense degenerate, that they no longer behave 

 like the other chromosomes in the rest stages; but they would appear to be special- 

 ized for a metabolic function. Thus it might be that in the insects the chromatin 

 nucleoli are those chromosomes which exert a greater metabolic activity than the 

 other chromosomes, or which carry out some special kind of metabolism; and from 

 this point of view they would certainly seem to be much more than degenerate 

 organs." Then I pointed out that not infrequently they are attached' regularly to 

 plasmosomes ; and now I would call attention to the fact that they are still more fre- 

 quently in contact with the nuclear membrane. Undoubtedly their function must be 

 very different from that of the autosomes, because they appear and behave so difterent 

 from them. The retention of the compact form and safraninophilous stain, so charac- 

 teristic of many of them, throughout the growth period and in the rest stage of the 

 spermatogonia, indicates that their nucleinic acid constituent changes less than in the 

 autosomes. The sex determination by them, reasoned by INIcClung, Miss Stevens 

 (19U56) and Wilson (1906), is a secondary function; if they do exercise a differentia- 

 tion of sex this would be not their primal function but rather an indirect result of 

 their metabolic peculiarities. From their position within the cell there can be little 



