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bulletin: museum of comparative zoology. 



According to my interpretation of the Vierergruppen in Calopte- 



nns, the formula would be -j a , > . Both the divisions following the 



formation of a Vierergruppe would therefore be reductions, and it would 



be quite immaterial whether the first di- 

 vision gave rise to two cells a b and c d, 

 or to the two cells a c and b d. In Calop- 

 tenus the rings may be placed upon the 

 spindle equator in either of the two posi- 

 tions l'epresented in Diagrams 1 and 2. 



This offers, perhaps, an explanation and 

 reconciliation of the contradictory views 

 of Henking, Hertwig, Hacker, and others. 

 As has been said, Henking holds that the 

 first division is a reduction division, and 

 the second an equation division, while most authors make the first an 

 equation, and the second a reduction division. Henkiug ('91) did not, 

 in his Pyrrhocoris paper, recognize the existence of Vierergruppen 

 as a regular stage in maturation ; but I feel justified by his Figure 20 

 in believing that they were really present in Pyrrhocoris, just as in 

 Gryllotalpa, Caloptenus, etc. Now, supposing the proper formula for 



the Vierergruppen to be ] , , [, why might it not happen in dif- 

 ferent nuclei, or in different chromatic groups of the same nucleus, that 

 one group should divide thus, — , and another thus, , , 1 Henking 



must assume that all the gi-oups are arranged on the spindle so as to 

 separate the non-identical idants by the first division. Hacker says : 

 " In der zweiten Richtungstheilung erfolgt dann die definitive Trennung 

 der nichtidentischen Idantenpaare." 



The following diagrams may illustrate these positions : — 



I. 

 a a 



b b 



Diagram I. illustrates Henking's view of the first division interpreted 

 according to the scheme of the Vierergruppen. All the groups would 

 thus suffer reduction division. 



