THE EFFECTS OF CENTRIFUGAL FORCE UPON THE 

 EGGS OF SOME CHRYSOMELID BEETLES^ 



R. W. HEGNER 



With Twenty-Foir Figures 



contexts 



I Introduction 507 



II Material and methods 508 



III The orientation of the eggs of Calligrapha bigsbyana 510 



IV The effects of gravity upon the development of the eggs of insects 511 



V A brief account of the normal embr)'onic development of Calligrapha bigsbyana 512 



VI The structure of the egg of Calligrapha bigsbyana at the time of deposition 516 



VII The effects of centrifugal force upon eggs centrif uged after deposition 517 



VIII The effects of centrifugal force upon eggs laid by centrifuged beetles 538 



1 Experiments with C. bigsbyana 538 



2 Experiments with Leptinotarsa decemlineata 539 



IX Review of the effects of centrifugal force upon developing eggs 540 



1 The distribution of the egg contents 54° 



2 The restitution of the egg substances after centrifuging 54^ 



3 The age of the egg when centrifuged 547 



4 The rate of development 547 



5 Eggs centrifuged before deposition 54^ 



X Summary 54^ 



XI Literature 550 



I INTRODUCTION 



It has been found that insect eggs are definitely oriented within 

 the ovaries and the exact position of the future embryo seems to 

 be determined already at this early period. This fact has led 

 many embryologists to believe that the eggs of insects are very 

 highly organized. If this is true a redistribution of the contents 

 of the egg would have a profound effect upon the development of 

 the embryo. In order to obtain a rearrangement of material a 

 centrifugal machine was used successfully, as is shown by the 

 experiments described in Part VII of this paper. 



1 Contributions from the Zoological Laboratory of the University of Michigan. No. 125. 

 The Journal of Experimental Zoology, vol. vi, no. 4. 



