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Notes on the Accessory Chromosome. 
By C. E. Mc Cuvne. 
Almost all recent papers upon insect spermatogenesis have con- 
tained more or less definite references to a chromatic element which 
differs in a marked way from the ordinary chromosomes. Early ob- 
servers of this structure noted it as a variety of nucleolus, but lately 
its true chromatic nature has been recognized. In pursuing a study 
of the spermatogenesis of Xiphidium fasciatum, I discovered 
this element to be a prominent and striking member of the germinal 
mitoses and, after careful study, became convinced of its importance. 
Its history in the testes of this animal, I described in a preliminary 
paper under the [title “A Peculiar Nuclear Element in the Male Re- 
productive Cells of Insects”, Zool. Bull., Vol. 2, No. 4. Further work 
upon the complete spermatogenesis of Xiphidium was later post- 
poned upon discovering that the male cells of the Acridian genus 
Hippiscus are larger and better adapted to a study of the finer 
details of the maturation mitoses. The results of my investigations 
upon this and other genera of the Acrididae indicated that the im- 
portance of the element observed in the Locustid cells had not been 
overestimated. The conclusions derived from this second investigation 
were embodied in a paper entitled “The Spermatocyte Divisions of 
the Acrididae”, Kans. Univ. Quart., Vol. 9, No. 1. 
My own work had been concerned almost exclusively with the 
spermatocyte mitoses and, feeling the need of information concerning 
the nature of the element in the spermatogonia, I induced one of my 
students, Mr. W. S. Surron, to undertake an investigation which might 
supply the desired knowledge. His results may be found in an ar- 
ticle: “The Spermatogonial Divisions of Brachystola magna”, in the 
Kans. Univ. Quart., Vol 9, No. 2. 
Meanwhile the work of PAULMIER and MONTGOMERY had shown that 
HENKING’s observations upon Pyrrhocoris were largely true of the 
Hemiptera in general, and further confirmed many facts that I had 
noted in the Orthopteran families. With the accumulating observations, 
it seemed desirable, for the purpose of attaining some uniformity, to 
bring together the work of the different investigators for comparison. 
This I have attempted to do, and the results of my labors will be 
