As outdoor work, look for the egg masses on trees and fences and devise means of combating the tussock-moth. Gathering and destroying the egg masses during the winter is found to be fairly effective in checking these insects. Since the cocoons frequently contain parasites that prey upon the larvae, it is advisable that only the cocoons that have egg masses attached to them should be destroyed; the others are harmless and may contain the useful parasites. The egg masses may be kept over winter in a box in a cool place, and the hatching of the tiny larvae and their subsequent rapid growth observed. POTATO BEETLE The eggs of this beetle may be found in early summer in clusters on the under surfaces of the leaves of potato plants. EGG.--Observe the size, colour, shape, position, and number in a cluster; appearance of head from outer end after a week. LARVA.--Observe the colour, shape, head, legs, voracious appetite, movements, rapid growth, destructiveness. PUPA.--Observe the larvae disappear from the plants; a search underground reveals the resting stage, or pupae. After ten days, the adult beetles emerge. ADULT.--Observe the colour, the hard shell covering the head; the hard outer wings and membraneous inner wings; the hard shell on the under surface of the body; the feelers, and legs. Why will spraying with a poison, such as paris-green, kill these insects? REFERENCES Dearness: _How to Teach the Nature Study Course Stories in Agriculture, Bulletin No. 124._ FISH The Nature Study lessons must be based upon observations of the living fish, preferably in May or June, September or October. The best place for this is on the bank of a clear stream from which it is possible to observe the fish in their natural environment. Here their life activities, their struggles, their conquests, and silent tragedies are enacted before the eyes of the observer. Many observations may be made in this way which will create a life-long interest in these reticent, yet active creatures. Since this method of study is practicable in but few cases, the study of the living fish in the aquarium is the best available substitute. The teacher or the boys of the class can catch a few fish of three or four inches in length and carry them in a jar of water to the aquarium. Minnows, chub, perch, catfish, or other common forms will do. OBSERVATIONS I The general shape, and the suitability of the shape for swimming. The surface of the body and the protection it affords. Note the scales and the slime, the latter a protection against the growth of fungi, etc. The gills--two openings behind the flaps at the rear of the head. The colours, and their value in concealing the fish. The dark upper surface makes it inconspicuous from above; the light under surface blends with the shadow and dims it. The divisions of the body--head, trunk, and tail. Movements of the fish and the part that the various fins play in these movements.