2OO KATHARINE FOOT AND E. C. STROBELL. 



It is interesting that such an experienced student of the 

 cytology of the Hemiptera as Gross ('12) should also find that 

 there are facts in Anasa tristis that are out of harmony with the 

 theories. He writes: 



"Spater bin ich dann durch die Freundlichkeit der Herrn 

 Dr. E. R. Downing noch in den Besitz einiger Praparate von 

 Anasa tristis gelangt, deren Studium mir gleichfalls zeigte, das 

 Wilson's Theorie mit den Tatsachen schwer vereinbar ist." 



Nucleolus.- In the few Hemiptera we have studied we have 

 interpreted the chromatin nucleolus of the first spermatocyte as 

 the homologue of the nucleolus of other forms. 



This is due to the fact that we have failed to find any other 

 structure in the cell which we have felt justified in interpreting 

 as a nucleolus. We were wrong in interpreting the chromatin 

 nucleolus in Anasa tristis as independent of the accessory chromo- 

 some, an interpretation we were first led to doubt in our study 

 of E. variolarius '09, and we stated in giving our results in this 

 form that we would reserve the publication of the evidence until 

 we could control it by a comparison with other forms. Buchner's 

 work ('09) on the accessory chromosome enabled us to harmonize 

 our conflicting evidence on this point. We wrote: "In this 

 paper Buchner's observations on the accessory chromosome 

 appear to throw some light on certain conflicting facts observed 

 by us in Euschistus variolarius. Buchner supports Wassilieff 

 in observing that only part of the substance of the chromatin 

 nucleolus gives rise to the accessory chromosome. This would 

 seem to indicate that the chromosomes in question are evolved 

 from a nucleolar mass of chromatin, thus homologizing this 

 structure with the cases in which it is claimed all the chromo- 

 somes are evolved from a large nucleolus, leaving a nucleolar 

 residue after the chromosomes are formed. In Euschistus we 

 find cases in which both the idiochromosomes and a chromatin 

 nucleolus are present at the same time. Such facts, added to 

 those cases in which the size relations of the chromatin nucleolus 

 do not agree with those of the idiochromosomes, raise the question 

 as to the identity of the two structures, though these facts would 

 not conflict with homologizing the chromatin nucleolus with the 

 nucleolus, which in some forms is said to give rise to all the 

 chromosomes.' 



