Ill ON ANIMAL LIFE 105 



familiar no such question intrudes. Among 

 quadrupeds and birds, fishes and reptiles, 

 there is no difficulty in deciding whether a 

 given organism is an individual, or a part of 

 an individual. Nor does the difficulty arise 

 in the case of most insects. The Bee or But- 

 terfly lays an egg which develops successively 

 into a larva and pupa, finally producing Bee 

 or Butterfly. In these cases, therefore, the 

 egg, larva, pupa, and perfect Insect, are re- 

 garded as stages in the life of a single indi- 

 vidual. In certain gnats, however, the larva 

 itself produces young larvae, each of which 

 develops into a gnat, so that the egg produces 

 not one gnat but many gnats. 



The difficulty of determining what consti- 

 tutes an individual becomes still greater among 

 the Zoophytes. These beautiful creatures in 

 many cases so closely resemble plants, that 

 imtil our countryman Ellis proved them to be 

 animals, Crabbe was justified in saying — 



Involved in seawrack here we find a race, 

 Which Science, doubting, knows not where to place ; 

 On shell or stone is dropped the embryo seed. 

 And quickly vegetates a vital breed. 



