Vol. XX. April, 1911. No. 5. 



BIOLOGICAL BULLETIN 



EXPERIMENTS WITH CHRYSOMELID BEETLES. 



III. THE EFFECTS OF KILLING PARTS OF THE EGGS OF 

 Leptinotarsa decemlineata. 1 



ROBERT W. HEGNER. 



CONTENTS. 



1. Introduction 237 



2. Killing the germ cell determinants 240 



3. Killing the primordial germ cells 243 



4. Killing parts of freshly laid eggs 244 



5. Killing parts of eggs in the blastoderm stage 245 



6. Killing parts of young embryos 247 



7. Killing parts of old embryos 250 



8. Summary 250 



i. INTRODUCTION. 



The method used in the experiments described in this paper, 

 i. e., killing parts of the egg, has been employed by a number of 

 investigators in many ways and for many purposes. Heat and 

 electricity are the agents which have been most frequently 

 applied. So far as I know insects' eggs have heretofore never 

 been operated upon in this way. The results obtained by the 

 use of these agents are quite similar to those so frequently brought 

 about by removing parts of the egg or embryo, or by isolating 

 blastomeres. The latter process is of course impossible in the 

 case of the insect's egg, since cleavage is superficial, but material 

 has been removed successfully .from different parts of beetles' eggs 

 in various stages of development. 2 



Three years ago a preliminary report was made of experiments 

 in removing portions of the eggs of Calligrapha multipunctata, 



1 Contributions from the Zoological Laboratory of the University of Michigan, 

 No. 131. Parts I. and II. of "Experiments with Chrysomelid Beetles" appeared 

 in the BIOLOGICAL BULLETIN, Vol. XIX., June, 1910, pp. 18-30. 



237 



