THE 



AMERICAN NATURALIST 



Vol. LI. November, 1917 No. 611 



THE GENESIS OF TPIE ORGANIZATION OF THE 

 INSECT EGGi 



PROFESSOR ROBERT W. HEGNER 



ZooLOGiCAi, Laboratory, Uxiversitt of Michigan 



I. The Complexity of Organization of the Insect Egq 



1. Introduction 



The morphological and experimental investigations of 

 the germ-cell cycle in insects which the writer has carried 

 on during the past ten years have resulted in the accumu- 

 lation of many data which indicate the complexity of or- 

 ganization of the eggs of these animals, and suggest 

 hypotheses regarding the nature and genesis of this or- 

 ganization. That the animal egg at the time develop- 

 ment begins does not consist of a homogeneous mass of 

 protoplasm, as the old theory of epigenesis required, but 

 is a highly organized cell containing various kinds of 

 protoplasm localized in definite regions has been proved 

 conclusively by numerous investigators working with the 

 eggs of many different species. The degree of organiza- 

 tion at the time of fertilization varies according to the 

 species of animal, but all embryologists admit that the 

 insect egg is one of the most highly organized of all. 



The nature and genesis of the different kinds of proto- 

 plasm in the insect egg is the principal problem discussed 

 in the following pages. This problem is the logical suc- 

 cessor of those dealing with cell lineage and the organiza- 

 tion of the egg at the time development begins. The re- 



1 Presented to the Johns Hopkins Scientific Association on October 9, 

 1917. 



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