ALIMENTARY TRACT OF CULEX PIPIENS 617 



SUMMARY AND CONCLUSION 



1. During metamorphosis in Culex pipiens, the number of 

 chromosomes in the cells of the pupal intestine is considerably 

 increased. 



2. Before disintegration of the cells begins, the chromosomes 

 of each pupal gut cell pass through a number of longitudinal 

 di\dsions resulting in three or four multiplications. 



3. The number of chromosomes in the multiple complex is 

 always a multiple of three — oftenest twelve, twenty-four, forty- 

 eight ; but frequently nine, eighteen, thirty-six, and even seventy- 

 two may appear. 



4. The triplex divisions of the chromosomes apparently arise 

 through premature spUtting of one member of each pair of chro- 

 mosomes in the original complex or by a precocious division of 

 one of each of the homologous elements of the bivalent chro- 

 mosomes. 



5. -The size relation between nucleus and cytoplasm is ex- 

 tremely variable. 



6. It appears that in the resting stage of those cells of normal 

 size which contain multiple complexes, there must be an accel- 

 erated growth of each chromatin thread which splits into normal 

 sized chromosomes in prophase, or else the cytoplasm of such 

 cells must fail to divide and to grow while the chromosomes 

 continue to do both. The former seems to be the probable 

 explanation. 



7. There is evidence of a parasynaptic union of sister chromo- 

 somes in the resting stage, followed by re-separation through 

 longitudinal splitting in the prophase. 



8. These sister chromosomes, the multiples of each member 

 of the original complex, tend to remain together throughout the 

 mitotic changes. 



9. The individuality of the chromosomes is maintained until 

 the cell disintegrates. 



10. The disintegrated cells appear to be digested by the cells 

 of the newly formed hning of the adult alimentary tract. 



