the Larva of Anopheles maculipennis, Meigen. 293 
The mouth-parts together enclose a space or chamber, at the 
posterior end of which is situated the mouth itself. The epi- 
pharynx forms the roof of this chamber, the mandibles form the 
sides, and the maxillae, together with the labial plate, the floor. 
The fore-gut is divisible into pharynx and oesophagus. An 
elaborate pharyngeal musculature was described, and the author 
believed that it is principally concerned with the process of 
swallowing. The oesophagus is prolonged backwards into the 
cavity of the mesenteron in the form of an oesophageal valve and 
a circular blood sinus is present in relation with the latter. The 
mesenteron consists of a cardia or outer wall enclosing the 
oesophageal valve, a ring of eight coeca, and the stomach. A peri- 
trophic membrane is present and its seat of origin is believed to 
lie in a special area of greatly enlarged gland cells, which are 
situated at the commencement of the mesenteron. 
The hind-gut is divisible into three regions, viz. ileum, colon 
and rectum, and the ileum receives at its commencement five 
malpighian tubes. 
The respiratory organs consist of the tracheal system, and pos- 
sibly of the two pairs of anal processes situated around the hinder 
extremity of the body, which may be of the nature of gills. The 
tracheal system communicates with the atmosphere by means of 
a single pair of spiracles located on the dorsal aspect of the eighth 
abdominal segment. It is, therefore, an example of the meta- 
pneustic arrangement. There are two principal longitudinal 
trunks, lying one on either side of the mid-dorsal line of 
the body. These vessels run from the spiracles directly forwards 
into the thorax. In the latter region each trunk divides into 
a pair of branches which supply the various organs of the head : 
and in the abdomen the branches of the tracheal system 
maintain to a large extent a segmental arrangement. In the 
region of the eighth abdominal segment the two main trunks 
give off a great number of small branches along their inner and 
ventral aspects. These branches pass to the wall of the terminal 
chamber of the heart and, on account of the thinness of the walls 
of their ultimate capillaries, it seems very probable that bv this 
means the blood is brought into close contact with the oxygen 
contained in them, and in this way a kind of “ lung ” is formed. 
A similar arrangement was found to occur in the larvae of Dura 
and Gulex, and reasons were given which suggest that it may be 
correlated with a metapneustic tracheal system. 
The anal gills consist of two pairs of delicate leaf-like out- 
growths of the integument situated around the anus. The 
cavities of the gills are in flee communication with the general 
haemoccelic cavity of the animal and contain, in addition to blood, 
fine tracheal branches. They are invested with a very thin integu- 
