498 POPULAR SCIENCE MONTHLY. 



seeds being ripened and the bud scales formed over the tender 

 tips of the branches long before the first severe frost appears. 



Let us now glance at those higher forms of life called animals 

 "higher," because they are absolutely dependent upon plants 

 for their food and see how they pass away their time while their 

 food-producers, the plants, are resting. 



Beginning with the earthworms and their kindred, we find 

 that at the approach of winter they burrow deep down where the 

 icy breath of the frost never reaches, and there they live during 

 the cold season a life of comparative quiet. That they are ex- 

 ceedingly sensitive to warmth, however, may be proved by the 

 fact that when a warm rain comes some night in February or 

 March, thawing out the crust of the earth, the next morning 

 reveals the mouths of hundreds of the pits or burrows of these 

 primitive tillers of the soil in our dooryard, each surrounded by 

 a little pile of pellets, the castings of the active artisans of the pit 

 during the night before. 



If we will get up before dawn on such a morning we can find 

 the worms crawling actively about over the surface of the 

 ground, but when the first signs of day appear they seek once 

 more their protective burrows, and only an occasional belated in- 

 dividual serves as a breakfast for the early birds. 



The eyes of these lowly creatures are not visible, and consist 

 of single special cells scattered among the epidermal cells of the 

 skin, and connected by means of a sensory nerve fiber with a 

 little bunch of nervous matter in the body. Such a simple visual 

 apparatus serves them only in distinguishing light from dark- 

 ness, but this to them is most important knowledge, as it enables 

 them to avoid the surface of the earth by day, when their worst 

 enemies, the birds, are in active search for them. 



The fresh- water mussels and snails and the crayfish burrow 

 deep into the mud and silt at the bottom of ponds and streams 

 where they lie motionless during the winter. The land snails, in 

 late autumn, crawl beneath logs, and, burrowing deep into the 

 soft mold, they withdraw far into their shells. Then each one 

 forms with a mucous secretion two thin, transparent membranes, 

 one across the opening of the shell and one a little farther within, 

 thus making the interior of the shell perfectly air-tight. There 

 for five or six months he sleeps free from the pangs of hunger 

 and the blasts of winter, and when the balmy breezes of spring 

 blow up from the south he breaks down and devours the protect- 

 ing membranes and goes forth with his home on his back to seek 

 fresh leaves for food and to find for himself a mate. 



Next in the scale come the insects, which comprise four fifths 

 of all existing animals, and each one of the mighty horde seen in 

 summer has passed the winter in some form. One must look for 



