288 



ZOOLOGY 



the change from larva to ^adult a series of moultings of the 

 chitinous covering is usually necessary; these may be accom- 

 panied or preceded by periods of rest, in which important in- 

 ternal changes take place. The metamorphosis is more common 

 among insects (Figs. 142 and 148), although a similar thing 

 happens in many of the Crustacea (as crabs, Figs. 128 to 130). 

 In spiders the development is direct. The eggs of many insects 

 hatch as worm-like larvae (grubs, maggots, caterpillars). These 

 are usually active, voracious, fat-storing animals, which after 



FIG. 129. 



FIG. 129. Megalops of Cancer irroratus. From Verrill. X 15. 



Questions on the figure. Compare with Pigs. 128 and 131, and make note of 

 the chief points of contrast. Compare also with adult crab (Fig. 130). What 

 differences are to be noted between the development in the lobster and in crabs? 

 Is the larval or adult crab more like the lobster? 



a period pass into a resting condition, often surrounding them- 

 selves with protective coverings (cocoons) . During this quiescent 

 stage they are described as pupcz. In the pupal stage the accu- 

 mulated fat is used by the organism in forming the new organs 

 of the adult or imago. The internal larval organs may be torn 

 down completely by the aid of amoeboid cells and be made to 

 contribute material to rebuild the new. The extent of these 



