No. 611] GENESIS OF ORGANIZATION OF INSECT EGG 649 



(b) Results of Experiments ivith Gravity and Centrif- 

 ugal Force.— A chrysomelid beetle, such as Calligrapha 

 or Leptinotarsa, during the process of egg-laying clings 

 to the under side of a leaf and the end of the egg that 

 emerges first is glued to the leaf by a viscid secretion. 

 Then the egg is pushed back away from the abdomen and 

 another is laid^^ (Fig. 5). In this way from four to 



eighty eggs are laid in one group within a period of about 

 an hour. These eggs hatch in approximately five days. 

 A few hours before they hatch the young can be seen dis- 

 tinctly through the semi-transparent egg shell. An exam- 

 ination of hundreds of eggs at this stage in their develop- 

 ment has established the fact that the posterior end of the 

 egg is attached to the leaf and the anterior end is free. 

 In every other respect the orientation of the young in 

 the egg corresponds to that of the egg as it lay within the 

 body of the mother before deposition; that is, the ends 

 and various surfaces of the egg are definitely determined 

 before deposition and correspond to the orientation of the 

 mother as indicated in the diagram (Fig. 5). This rigid 

 correspondence between the orientation of the egg and 

 that of the adult is known as the ''law of orientation" 

 which was first discovered by Hallez in 1886. 



Since the eggs of these beetles are usually attached to 



13 Hegner, 1909, Joum. Exp. Zool., Vol. 6. 



