THE EGG. 11 



mation of the embryonic caterpillar ; we merely 

 know that nothing essentially different transpires 

 from what occurs in other insects ; the yolk-mass 

 first breaks up/into an infinite number of cells, 

 and then those lying next the surface enlarge, 

 and form what is to be the germinal layer, a 

 specialized band of nucleolated cells nearly en- 

 circling the egg and out of which the future cat- 

 erpillar develops. The first step in this latter 

 process is the division of the band by cross in- 

 dentations' into a number of segments, while at 

 the same time the anterior portion increases in 

 size ; next, the rudiments of the various mem- 

 bers, such as the mouth parts and legs, scarcely 

 distinguishable in character one from another, 

 bud out from the sides of the body. Thus the 

 earliest form of the caterpillar may be called a 

 segmented ribbon, with lateral buds where the 

 movable organs are to be ; and this ribbon is 

 curled backward around the egg, head to tail. 

 By degrees the ribbon broadens and fills out, or 

 incloses the yolk-mass of the interior, the legs 

 and other appendages grow, the mass of the body 

 retreating at the same time to give them room, 

 until, when the time of hatching approaches, the 

 caterpillar has recovered its position in the egg, 

 but with its back and not its belly next the wall 

 of its prison. Finally, the circumference of the 

 egg becomes too contracted for the rapid growth 



