PROCESS OF nATCHING. 229 



it. The outer covering is easily ruptured, and is rendered all the more 

 fragile by freezing : but the inner covering is so tough that a very 

 strong pressure between one's thumb and finger is required to burst it. 

 How, then, will the embryon, which fills it so compactly that there is 

 scarcely room for motion, succeed in escaping from such a prison ? The 

 rigid shell of the bird's egg is easily cracked by the beak of its tenant ; 

 the hatching caterpillar, curled within its egg-shell, has room enough to 

 move its jaws and eat its w^ay out ; the egg-coverings of many insects 

 are so delicate and frail that the mere swelling of the embryon affords 

 means of escape; those of others are so constructed that a door flies 

 open, or a lid lifts by a spring, whenever pressure is brought to bear; 

 in some two halves open, as in the shell of a muscle; whilst in a host 

 of others the embryon is furnished with a special structure called the 

 egg-burster, the office of which is to cut or rupture the shell, and thus 

 afford means of escape. But our young locust is deprived of all such 

 contrivances, and must have another mode of exit from its tough and 

 sub-elastic prison. Nature accomplishes the same end in many differ- 

 ent ways. She is rich in contrivances. The same warmth and moisture 

 which promote the development of the living embryon also weaken the 

 inanimate shell, by a process analogous to decomposition, and by a gen- 

 eral expansion consequent upon the swelling of the embryon within. 

 Thus, the eggs when about to hatch are much more plump and some- 

 what larger and more transparent than they were when laid. At last, 

 by the muscular efforts of the nascent locust, and the swelling of its 

 several parts, especially about the head and mouth, the shell gives way, 

 generally splitting along the anterior ventral part. The whole process 

 may, in fact, be likened to the germination of a hard-covered seed, when 

 planted in moist ground, and, precisely as in this latter case, there is 

 in some loose soils a certain heaving of the ground from the united swell- 

 ing of the locust eggs. All the eggs in a given mass burst very nearly 

 at one and the same time, and in that event the lowermost individuals 

 await the escape of those in front of them, which first push their way 

 out through the neck of the burrrow (Fig. 4, d) provided by the parent. 



"They all escape, one after the other, through one small hole, which 

 in the field is scarcely noticeable. Such is the usual mode of hatchmg; 

 but when the young from the lower eggs hatch first, or when the upper 

 eggs perish and leave the lower ones sound — as is not unfrequently the 

 case — the exit is nevertheless easily made along the channel already 

 described (Fig. 4, c)."^^ 



When once the shell is ruptured the nascent larva soon succeeds, by 

 a series of undulating movements, in working free therefrom and making 

 its way to the light in the manner just described. Once on the surface 

 of the ground it rests for a few minutes, generally lying on the side. 

 Its members are still limp and directed backward, and it is yet enveloped 



35 For fnller details rpspecting the mode of the escape of the nascent locust from the egg, the reader 

 Is referred to Chapter IX. 



