ALIMENTARY TRACT OF CULEX PIPIENS 609 



Mawr Laboratory. This material has proved favorable for 

 the study of all somatic tissues as well as of the gei'm cells. It 

 includes sections of a large number of individuals in which vari- 

 ous parts of the alimentary tract are undergoing metamorphosis. 



PREVIOUS OBSERVATIONS OX THE ALIMENTARY TRACT OF CULEX 



M. T. Thompson has described in detail the changes which 

 take place during the metamorphosis of the digestive tract of 

 the mosquito. But while he notes the fact that mitotic iigures 

 are very numerous toward the end of these changes, he does 

 not discuss the complexes. 



Miss Monica Taylor, while seeing the great importance of 

 working out the somatic complexes thoroughly, seems to have 

 been handicapped by a difficulty in finding dividing somatic 

 cells. She makes no mention of any variation in the number 

 of chromosomes in the gut tract, and her figures show only 

 cells previous to the beginning of metamorphosis or after its 

 completion. 



In fact, in all the work which has been done upon the chromo- 

 somes of Culex, observers have overlooked, or at least have 

 failed to mention, an interesting phenomenon which occurs in 

 connection with metamorphosis of the gut tract — the appearance 

 of multiple complexes in cells which are about to give place to 

 the new adult tissue. 



BEHAVIOR OF THE GUT CELLS DURING METAMORPHOSIS 



During the pupa stage, the entire gut, posterior to the oesoph- 

 agus, undergoes metamorphosis. The larval tract degenerates 

 and is absorbed, while the new tract is formed from cells, the 

 nuclei of which appear between the bases of the larval cells. 

 As the new epithelium forms, a marked activity develops in the 

 old cells. There is some cell division accompanied by rapid 

 multiplication in the number of chromosomes. While the 

 normal somatic number in material prepared by the ordinary 

 methods, is apparently three, as Miss Taylor ('14) states, the 

 constant occurrence of splits in these chromosomes gives weight 



JOURNAL OF MORPHOLOGY, VOL. 29, NO. 2 



