198 Edmund B. Wilson 



artige Irregularitaten vorkamen, diese sich wohl auf lange hinaus 

 erhalten miissten, so dass unter Umstanden Falle mit ausserordent- 

 lich grosser Variabilitat der Chromosomenzahl zur Beobachtung 

 kommen konnten, ohne dass selbst diese das Grundgesetz umstos- 

 sen vermochten, welches lautet: Es gehen aus jedem Kerngeriist 

 so viele Chromosomen hervor als in die Bildung derselben 

 eingegangen sind" ('90, p. 61). To the earlier expression of 

 this "Grundgesetz" Boveri has recently added the statement 

 that the chromosomes that emerge from the nucleus are not merely 

 of the same number but also show the same size-relations as those 

 that entered it. "Was durch den kurzen Ausdruck "Individuali- 

 tat der Chromosomen" bezeichnet werden soil, ist die Annahme 

 dass fur jedes Chromosoma, das in einen Kern eingegangen ist, 

 irgend eine Art von Einheit im ruhenden Kern erhalt, welche der 

 Grund ist, dass aus diesem ruhenden Kern wieder genau ebenso 

 viele Chromosomen hervorgehen und dass dieses Chromosomen 

 iiberdies da, wo vorher verschiedene Grossen unterschieden waren, 

 wieder in den gleichen Grossenverhaltnissen auftreten" ('07, p. 229). 

 The facts seen in Metapodius and other insects are thoroughly 

 in accord with the foregoing statement, and justify the additional 

 one that the chromosomes conform to the same principle in respect 

 to their characteristic modes of behavior. In the Hemiptera 

 heteroptera generally the idiochromosomes and supernumeraries, 

 the ra-chromosomes, and the "ordinary chromosomes" or "auto- 

 somes" show each certain constant peculiarities in respect to the 

 time of synapsis and behavior during the growth-period, and 

 assume a characteristic (though not entirely constant) mode of 

 grouping in the first spermatocyte. Perhaps the most obvious 

 of these facts is the very early condensation of the idiochromo- 

 somes and supernumeraries in the growth-period as contrasted with 

 the other chromosomes; and in the case of Pyrrochoris I have 

 shown ('09) that the idiochromosome never assumes a diffuse con- 

 dition after the last spermatogonial division. But even more 

 significant are the definite differences shown in the couplings of the 

 various forms of chromosomes that take place in the course of 

 the spermatogenesis. Nothing in these phenomena is more 

 striking than the accuracy with which these couplings take place. 





