Miarvels of 
in the pools left by the overflowing of the 
Nile. That the land of Goshen should have 
been exempt lends support to this theory, for 
that country is a rather higher, dry, grazing 
district, not subject to be overflowed, and, 
consequently, would not serve as a breeding- 
ground for the “ flies.” 
Gnats are particularly suitable subjects for 
the study of life-history and development, for 
they are common and easily procured in all 
stages; they require very little care while 
under observation ; and, finally, their life-cycle 
is fairly quickly run through. The periect 
insects are found from early summer onwards ; 
even during the winter the hibernating females 
may be seen in numbers on the roofs and 
walls of cellars and outhouses. To begin at 
the beginning, the eggs are readily found as 
little brown boat-shaped masses floating on 
the surface of any open water-butt ; with 
a little patience, the Gnat may be observed 
preparing the raft. Resting usually on the 
edge of some floating object, or sometimes on 
the surface of the water, with her hind legs 
she arranges the eggs side by side in such a 
manner that each egg is upright, with one 
end exposed to the air and one end in the 
water. As each egg tapers slightly towards 
the upper end, the resulting egg-mass forms 
a slightly concave raft, which in case of acci- 
dent is self-righting, so that it always floats 
with the hollow side up. In a few days the 
eggs hatch, the young larve escaping from 
their lower ends straight into the water. 
The larve wriggle actively about in the water 
by means of lashing their tails violently from 
side to side. They are almost black in colour, 
and when full-grown, about half an inch long. 
The head is attached by means of a distinct 
neck, and is furnished in front with a pair of 
feathery organs, with which it sweeps up the 
microscopic organisms upon which it feeds into 
the mouth. Behind, the neck is a conspicuous 
bulge, in which are situated the parts that give 
rise to the wings and legs of the fly. Near the 
tail is a moderately long, straight tube pointing 
directly upwards, the significance of which we 
shall see directly, and behind it is the fan of 
fine hairs which serves as a powerful oar. 
the Universe 907 
GNAT GRUB. 
The grub or larva of the Gnat floats at the surface of the 
water head downwards. It is shown here enlarged about 
eighteen times the natural size 
