286 ZOOLOGY. 



the aid of amoeboid cells and be made to contribute material 

 to rebuild the new. The extent of these changes can only 

 be realized by a comparison of the structure of a caterpillar 

 and of the butterfly into which it develops. The larvae may 

 be suited to aquatic life, the adult to aerial; the larva may be 

 carnivorous or herbivorous, the adult may live on the nectar 

 of flowers. These changes of habit are closely correlated with 

 the changes of structure noted in the metamorphosis. The 

 reproductive organs are not mature until the imago-stage is 

 reached. Frequently the imago only survives long enough 

 to insure the laying of fertilized eggs. 



FIG. 128. 



FIG. 128. Violet Land-Crab. After Shufeldt. 



Questions on the figure. Compare the crab with the lobster (Fig. 

 130) as to the development of the body-regions, segmentation, appendages, 

 etc. Compare all the figures of crabs available and note in what respects 

 they vary externally. 



'324. Library References. Make a report on the metamorphosis in 

 Crustacea. What is meant by an incomplete metamorphosis ? Illustrations. 



325. Ecology. When we remember the great number of 

 species and of individuals in the group of arthropods we are 

 forced to realize something of their importance in their rela- 

 tion to other forms of life on the earth. Their numbers and 

 their enormous power of reproduction make it inevitable that 



