THE CHROMOSOME COMPLEX OF CULEX PIPIENS. 299 
together side by side with homologous poles together, the 
opposite of what happens in the case of magnetic attraction. 
Such a hypothesis will account for the frequent occurrence 
of parasyndesis, and for the further accentuation of this 
into complete fusion as is supposed to take place in Culex 
pipiens. 
Summary. 
(1) The egg-rafts of Culex pipiens are laid most 
copiously between hours 10.30 p.m. and 12 p.m. They are 
also laid between 4 a.m. and 6 a.m. 
(2) Fertilisation in Culex pipiens is normal. Segmenta- 
tion begins in less than an hour after the deposition of the 
last egg. 
(3) The chromosome number in the segmenting nuclei 
is six. 
(4) A tendency to parasyndesis is exhibited by the seg- 
menting nuclei. 
(5) Parasyndesis probably effects the condition of the 
chromosomes in the nuclei of larva, pupa, and imago, i.e. 
is responsible for the presence of the apparently “ haploid ” 
character of the nuclei in the somatic cells. 
Note. — After the completion of the foregoing paper, 
Metz’s “ Chromosome Studies on the Diptera II. 
The Paired Association of Chromosomes in the D p- 
tera, and its Significance’, Mourn. Exper. Zool.’, xxi., 
came into my hands. 
With regard to certain criticisms passed on my work, 
I should like to state : — 
(1) The fixatives employed Jay me were precisely those 
employed by Metz (see p. 379, ‘Quart. Journ. Micros. Sci.’, 
vol. lx). 
(2) Although I have not specified this, all the precautions 
recommended by Metz to secure good fixation and penetra- 
tion were employed by me. I cannot, therefore, put my 
results down to bad fixation. 
