70 H. B. GOODRICH 



DISCUSSION 



A. The sex chromosorne complex 



It has been pointed out that the XY complex of Ascaris in- 

 ciirva comprises a greater number of chromosomes than any 

 hitherto recorded, the nearest approach being that of Ascaris 

 lumbricoides (Edwards '10) where are found five X elements 

 unmated by a Y, and that of Acholla multispinose (Payne '10) 

 in which case five X components are opposed by a single Y, but 

 in' this case the Y is equal to or larger than the combined X- 

 elements. It should be noted, however that the work of Kautzsch 

 ('13) and Geinitz ('15) on the somatic cells of Ascaris megalo- 

 cephala indicates that the single X-chromosome present in 

 the maturation division may be represented by 8 or 9 elements 

 in the somatic cells. In regard to mass of X-chromatin relative 

 to that of the autosomes it is more difficult to make compari- 

 sons based on inspection of the published. figures. In A. incurva 

 the numerical ratio of X-chromosomes to autosomes in the 

 spermatids is as 7 to 13 (disregarding the microsome) or about 

 1 to 2, and this may be considered as roughly proportional to 

 the mass. This mass ratio may be equalled or even surpassed 

 by that of Protenor where the single X-element is of relatively 

 great size. Among other nematodes thus far examined with 

 the exception of Ascaris lumbricoides the X-element is single 

 and also unopposed by a Y, but the ratio of mass to that of the 

 other chromatin is high (Mulsow '12, Gulick '11, Edwards '12). 

 The possible significance of the large X-groups is discussed below. 



The behavior of the multiple XY-complex of Ascaris incurva 

 differs somewhat from that of other such compound glroups 

 found among the Hemiptera. In the former, the X-group 

 united by linin fibers, acts as a unit in the first maturation spindle 

 where the unequal division occurs, and a definite portion (one 

 end of the long X-component) as shown by position, structure 

 and attachment of fibers, is mated to the Y-chromosome ; in 

 the latter, for example Fitchia, Rocconota, Conorhinus, Prioni- 

 dus, Sinea, Gelastocoris and Acholla multispinosa (Payne 

 '09) and Thyanta calceata or Thyanta 'B' (Wilson '11), the 



