GERM CELLS IN ASCARIS INCURVA 73 



male, will give a basis for the typical mode of inheritance of 

 sex-linked characters, it may also be expected that within the 

 sex-linked group there would occur a redistribution of the char- 

 acters inherited from the respective parents. This redistribu- 

 tion would be more free than that shown by the 'cross-overs' 

 among the sex-linked characters in Drosophila (see Morgan, 

 Sturtevant, Muller, Bridges '15) because it would be based on 

 a random assortment of chromosomes of the X-group, rather 

 than on a transference of determinants between a single synaptic 

 pair of chromosomes, such as is the basis of the 'chiasmatype' 

 theory. 



B. The X -chromatin and the plasmasome 



One object of this work as planned was to trace, if possible, 

 the history of the X-chromatin through the growth stages of 

 the spermatocyte; and it had been anticipated that the X- 

 chromatin would be distinguishable as a compact chromatin 

 nucleolus or nucleoli similar to the conditions so clearly demon- 

 strated in many insects — for example; Wilson '05 a, b, '10, '11, 

 '12, Davis '08, and Payne '09. In the preliminary report it 

 was stated that "During the growth stages a part of the chromatin 

 is massed in a large irregular karyosome." This was from ob- 

 servations on material fixed in Gilson-Carnoy's fluid after which 

 this body takes an intense haematoxylin stain. A more de- 

 tailed study, however, has shown that this is a plasmasome, 

 often entwined or even penetrated by chromatin threads but 

 bearing no resemblance to the chromatic nucleolus of insects. 

 As has been outlined in the description this body takes plasma 

 stains while the threads upon its surface stain as chromatin. 

 A similar body is found in the inter-kinetic stages of the gonial 

 divisions ; it reappears in the growth stages and finally fragments 

 during the prophase forming a number of droplets in both oogene- 

 sis and spermatogenesis. The mass of the chromatin threads 

 or knots upon its surface in spermatogonesis is in no way com- 

 parable to that of the huge X-group nor is there in spermato- 

 genesis, at least, any tendency of the chromatin to concentrate 

 in masses resembling a nucleolus or comparable in number with 



