66 
possible. When at the end of the drag the net should be quickly 
lifted, otherwise half the captives will escape. The contents of the 
net must be turned out on the smoothest piece of ground available 
and be subjected to the strictest scrutiny, for manv of the most 
treasured specimens will lie motionless and quite hidden in the 
masses of weed dredged up. It is a good plan to have a supply of 
small tin boxes ready, each very loosely packed with wet weed. 
Beetles may be put into one, leeches into another, a third may be 
reserved for scorpions, and so on. If an assortment of these insects 
be carried any distance in water some of them will be sure to dis- 
appear down the throats of their more robust companions. The 
above method of packing will reduce this cannibalism to a minimum, 
for when out of water these insects seem to desire no food. 
VERMES ( Worm- like Creatures). 
Common Horse Leech. — The first few drags of the net are 
almost sure to bring out several of these leeches. Our illustration 
depicts a fairly large specimen crawling over the glass side of an 
aquarium, and shows the circular sucking discs which enable the 
creature to hold on to smooth surfaces. Leeches are very worm- 
like in appearance, and are capable of considerable expansion and 
contraction in length. When swimming they move rapidly through 
the water by a series of undulatory movements, suggesting some- 
what the action of an eel. The colour varies from a dult brown to a 
light yellow, according to the nature of the bottom of the pond. 
They are very hardy creatures, and will live in almost any aquarium 
under the most adverse circumstances provided the tank is kept cool. 
When in captivity they will readily take earthworms for food ; and 
as they are such expert climbers the tank containing them must be 
covered with some perforated material. 
MOLLUSCS. 
Freshwater Mussel. — For these molluscs we must search either 
in fair sized lakes or in rivers. In such situations they lie half buried 
in the mud and require the aid of the dredge to dislodge them. 
If one of these Swan Mussels, as they are sometimes called, be careful- 
ly examined, it will be found to possess two shells jointed together by 
an elastic hinge, and held tightly closed by the powerful adductor or 
closing muscles of the animal. But if it be placed in some vessel of 
water with a thick layer of sand on the bottom and left undisturbed, 
the mussel will, after a time, gradually separate the two valves and 
protrude a mass of yellow flesh known as the foot. This will slowly 
burrow into the sand and work the shell into a semi-upright position, 
as seen in our illustration. After the animal has buried about three- 
quarters of its shell and made itself quite at home in its new 
surroundings, a careful examination of the upper part will reveal 
two peculiar processes between the shells. These are the siphons 
which con'-tantly pass a current of water through the creature's body. 
The gills extract the oxygen, and the digestive apparatus filters off 
the microscopic green plants upon which the animal subsists. The 
inhalent siphon isfttrnished with a number of tentacles which guard 
the entrance and prevent the inflow of any inconveniently large 
particles. These mussels are capable of moving considerable 
distances, though their ploughing through the sand is very slow. 
Freshwater Winkle. — This water snail is fairly common in 
lakes and sluggish rivers in some parts of Britain, but it is very 
local. The shell is of a dull yellowish colour, marked with bands 
of purplish brown, and at first sight it looks very much like a big 
