THE CHROMOSOME COMPLEX OF CULEX PIPIENS. 289 
In the ‘ Proceedings of the Royal Society/ 1915, a full de- 
scription of the chromosome cycle of Coccidia and Gregarines 
appeared (Dobell and Jameson) (1), a work which elucidates 
a cytological condition of affairs superficially somewhat similar 
to that which obtains in Culex pipiens. The authors of 
that paper demonstrate the presence of the haploid number 
of Chromosomes at every nuclear division in the life-history 
of Aggregata and Diplocystis except in the zygote. 
In f Chromosome Studies of Diptera 5 (2), July, 1914, 
Charles W. Metz calls attention to the neglect of Diptera by 
students of cytology — a neglect all the more pronounced when 
contrasted with the great amount of energy expended upon 
other insect-groups — notably Hemiptera, Orthoptera, Coleop- 
tera. He offers, as a probable explanation of this neglect, 
the unsuitability of Dipterous material for cytological study 
and the great difficulties connected with such study. The 
results embodied in Metz’s paper, as will be shown later, have 
been helpful in interpreting the phenomena observed in 
Culex and in showing that there is no essential difference 
between it and other Diptera. 
Dr. Woodcock discovered that, after the summer female of 
Culex pipiens has fed once on the blood of a living bird, 
the eggs attain their normal size and are ready for fertilisa- 
tion. The raft is laid almost immediately after the second 
feed — fertilisation taking place in the interval between the 
two meals. This probably accounts for the fact that females 
reared in captivity and fed on a fruit diet appear never to be 
fertilised. 
Material and Methods. 
In the summer of 1915 cages similar to those described by 
Dr. Woodcock were set up in the College Laboratory of Notre 
Dame, Glasgow, young pigeons being employed as food. A 
pigeon was also caged in the near neighbourhood of a 
wooden tub stocked with larvse, and placed in a small garden 
at Notre Dame. Control experiments, which will be described 
