6 
THE ESSEX NATURALIST. 
tissue, and pass to the surface cells along definite tracks. No 
doubt the rhabdites give a considerable amount of support to 
the body and yet permit freedom of movement. They are 
analogous to an external skeleton, made up of small parts, which 
articulate freely—a variety of chain armour. Then, too, the 
rhabdites can be discharged, and on coming into contact with 
water, produce a slimy substance. In addition to this, planarians 
have special glands developed on the lateral margins, which 
produce mucus. This mucus serves as a protection and is used 
in the capture of prey. Sometimes threads of it are formed and 
are used by the animal to lower itself through the water. (See 
p. 2.) 
COLLECTION AND PRESERVATION. Planarians 
should be searched for in fresh water, under stones and on the 
shaded parts of submerged plants. Planaria alpina may be 
found in cold springs and mountain streams. Flowing streams, 
rivers, lakes and ponds are all suitable hunting grounds. 
Bdellocephala punctata lives in mud, which it leaves only for the 
purpose of depositing cocoons. Bohmig (3) suggests wrapping 
up bait, such as a dead frog, in gauze and leaving it in a pond 
or stream for a few days. 
When collecting planarians, care should be taken that no 
animals likely to die and set up decomposition remain in the 
tube containing them. The water must be prevented from 
becoming warm during transportation, as planarians soon die 
and disintegrate under sudden changes of temperature. 
Identification of species should be made, when possible, on 
living animals ; it is often difficult to diagnose dead specimens, 
especially when they are not sexually mature. 
Planarians do not make very satisfactory preparations, as 
they always contract, in spite of every care. Steinmann and 
Bresslau (36) recommend the following solution for killing :— 
Commercial nitric acid, 1 part : a saturated solution of mercuric 
chloride in a 5% solution of common salt, 1 part ; distilled water, 
1 part. The animal is placed on a sheet of glass with the smallest 
quantity of water possible. As soon as the planarian extends 
itself, the solution is poured over it quickly and the creature is 
left in the fluid not longer than one minute. It is then placed 
