94 



SEX-LORE 



These eggs first hatch into grubs or, in butterflies and 

 moths, into caterpillars (Fig. 37). The caterpillar feeds 

 and grows, casting its skin repeatedly. Before the last 

 moult, the caterpillar ceases to feed and wanders 

 about seeking a suitable place to settle on, before it 

 enters the next stage of the metamorphosis. Some 

 caterpillars suspend themselves to a branch of a tree 

 by a thread of silk which they have spun; others 



CH 



WD 



EW KS 



FIG. 36. HEN'S EGO : DIAGRAMMATICAL LONGITUDINAL, SECTION. 

 (After Allen Thomsen.) 



CH, Chalaza ; DM, vitelliue membrane ; Gl), yellow yolk ; 

 Bl, germinal disc with germinal vesicle ; WD, white yolk ; 

 EW, albumen ; KS, shell ; S, shell membrane ; LR, air 

 chamber. 



(From Weismann, "The Evolution Theory.") 



spin a cocoon of silk in which they are enclosed 

 (Fig. 38), whilst others, again, descend to the ground, 

 scoop out a dry burrow, and then go to sleep. Then 

 the last moult takes place; beneath the caterpillar's 

 skin a horny shell is formed, and as soon as this is 

 complete, the outer skin is cast off; and we have the 

 pupa or chrysalis. The chrysalis is motionless and 



