A CHROMATOID BODY SIMULATING AN ACCESSORY 

 CHROMOSOME IN PENTATOMA. 



EDMUND B. WILSON. 



A brief account will here be given of a body that first attracted 

 my attention in the spermatogenesis of Pentatoma (Rhytodolomia) 

 senilis Say, where it offers so deceptive a resemblance to an 

 accessory or unpaired JY"-chromosome that it might readily lead 

 to erroneous conclusions could not its entire history be followed 

 out in every detail. A body that is evidently of the same nature 

 but somewhat smaller was afterwards found in Pentatoma 

 (Chlorochroa) juniperina L., and in Podisns crocatus Uhler, where 

 it is still smaller. A similar body is often seen also in Ccenus 

 delius Say, but appears here to be of less constant occurrence. 

 Its behavior is essentially the same in all these cases, and I suspect 

 that it will be found in many other insects. It is probably of the 

 same general nature as the bodies that have been described by 

 various observers as "chromatoid Nebenkorper," "chromatoid 

 corpuscles," etc., in the spermatogenesis of vertebrates, insects, 

 and other animals. In Pentatoma senilis it is of very large size, 

 invariably present, and almost always single, though one or two 

 similar but smaller granules often appear also in the same cell. 

 Its constancy and conspicuous character in this species exclude 

 the possibility of error in its identification at any period save the 

 earliest. 



As seen during the growth-period and the spermatocyte- 

 divisions it is of rounded form, dense and homogeneous consis- 

 tency, and after double staining with hsematoxylin or safranin 

 and light green is at every stage colored intensely blue-black or 

 brilliant red, precisely like the chromosomes of the division- 

 period or the chromosome-nucleoli of the growth-period. In 

 the first spermatocyte-division it may lie anywhere in the cell, 

 sometimes almost at the periphery, but is often close beside the 

 chromosomes. In the latter case it usually lies in, on or near 

 the spindle, lags behind the chromosomes during the anaphases, 



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