310 
still distinct, and the section has struck the spot where the chitini- 
zation of the inner tube is most heavy. The inner tube is com- 
pounded by 6 pieces. The section has passed between two teeth of 
the ventral piece; in g and h they have just passed through one 
of the following saw teeth. Near the apex of the outer tube the 
walls are very thin and furnished with stronger chitin teeth. The 
section / has just passed through the mouth of the tube; the sec- 
tion shows, that there is only one spiracle in the Mansonia-larva 
(Raschke points out the same fact with regard to the Culex- 
larva). The section shows, further, that the one side of the outer 
tube is groove-shaped; the saw teeth may be moved to and fro 
in the groove. When pushing the inner tube forwards and back- 
wards within the outer tube the larva saws an opening in the 
plant tissue, which at the same time is pierced by the chitin thorns 
on the apex of the outer tube. 
If we will try to understand the peculiar modification of the 
sipho of the Mansonia enabling the tube to be used as a passage 
for the plant-air and, at the same time, as a piercing organ, we 
must regard the sipho of the Culicidæ more thoroughly. 
Originally the sipho of the mosquito larva carries on the apex 
6 chitinous elements surrounding the spiracle. We find an anterior 
piece, a pair of lateral flaps, and three posterior pieces. This 
arrangement is the most primitive found among the mosquito-larvæ; 
hitherto it is only known in the case of Anopheles. The breathing 
tube of the other mosquito larvæ has developed from this type; 
it has only five pieces. Especially Nuttal & Shipley7(1901 p. 
64) and H. D. K. (1912 p. 92) have contributed to the under- 
standing of this problem. Through the study of the sipho of Urano- 
tænia the last mentioned authors have tried to demonstrate that 
the large triangular plate of the Anopheles larva is identical with 
the peculiar stirrup-shaped piece within the tube of the Culex; 
through that piece the tracheæ communicate with the outer air. 
Unfortunately the authors give no drawings of the facts in Uran- 
otænia. The five flaps, surrounding the margin of the tube in 
most mosquito larvæ, correspond with the five other pieces in the 
Anopheles. Sections through the tube of Anopheles have convin- 
ced me of the correctnes of the opinion of H. D. K. 
If the figures 29 and 30, representing respectively a lateral 
and a dorsal view of the apex of a Culex-sipho, are compared with 
