RESULTS OF CROSSING TWO HEMIPTEROUS SPEClK-v 2OI 



If these investigators are right in claiming that the chromatin 

 nucleolus is in fact a chromosome which retains its individuality 

 and continuity through the growth period, then it is quite 

 necessary that another structure should be found in these cells 

 which can be homologized with the nucleolus of other forms. If 

 one is obviously not present, some plausible explanation of its 

 absence must be given. If it is not figured in drawings, then the 

 observer can be accused of superficial and careless observation; 

 but if it is absent in photographs, then the old scapegoat- 

 faulty technique is held responsible. 



This is McClung's explanation of the fact that a second 

 nucleolus is conspicuously absent from all our photographs of 

 the growth period of the spermatocytes of Anasa tristis. He 

 says: "Owing to the technique employed by them the plasmo- 

 some is practically destroyed." It is certainly highly improbable 

 that a method that has not destroyed the plasmosome in the 

 other forms we have studied should destroy this structure in 

 these Hemiptera. 



It is interesting to notice how the plasmosome of Anasa tristis 

 has developed and waxed strong since the earlier investigators 

 described and figured it. It was described as a pale body and 

 figured accordingly, but in Pinney's recent drawings it has 

 developed into a strong dense body fully as chromatic as the 

 chromatin nucleolus. Although Wilson himself describes it as a 

 "pale" body, McClung's photographs from Wilson's preparations 

 show that the structure which McClung interprets as a plasmo- 

 some is not a pale body, but is fully as chromatic as the chromatin 

 nucleolus. Here, as in other points where our conclusions are 

 condemned, we are willing to rest the case on a comparison of 

 McClung's photographs with ours. 



Our belief that the chromatin nucleolus of the Hemipter.a is 

 the homologue of those nucleoli of other forms that are said to 

 give rise to all the chromosomes has been greatly strengthened 

 by our study of the spermatogenesis of Euschistus crassus. In 

 this form there are two chromatin nucleoli, one of w r hich gives 

 rise to the idiochromosomes and the second gives rise to a pair 

 of autosomes the so-called ordinary chromosomes. 1 



1 These results were sent to press last February. 



