20O Edmund B. Wilson 



ADDENDUM 



The probability in regard to the female groups of Syromastes, 

 expressed in the footnote at p. 192 was first stated in my preced- 

 ing paper ('09, p. 73 ) after a study of the male only. Since the 

 present paper was sent to press I have had opportunity to ex- 

 amine females of this form. The facts are exactly in ac- 

 cordance with my prediction, the female groups containing 24 

 chromosomes, while the male number is 22. It now seems clear, 

 however, that the two idiochromosomes of Syromastes do not 

 correspond respectively to the large and the small idiochromo- 

 some of Metapodius or Lygaeus but are equivalent, taken together, 

 to the large idiochromosome or to the odd chromosome of 

 Anasa, etc. 



October 25, 1908. 



WORKS REFERRED TO 



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 BOVERI, Th. '90 Zellenstudien. III. Ueber das Verhalten der chromatischen 



Kernsubstanz bei der Bildung der Richtungskorper und bei der Be- 



fruchtung. Jena, 1890. 

 '07 Zellenstudien. VI. Die Entwicklung dispermer Seeigel-Eier, etc. 



Jena, 1907. 



FICK, R. '05 Betrachtungen iiber die Chromosomen, ihre Individuality, Reduc- 

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