110 GEORGO ORIHAY SHINJI 



of certain Orthoptera. He did not state how the eggs were 

 infected, but thought it was a case of symbiosis. The occurrence 

 of non-hving substances has also been recorded in the eggs of 

 several Diptera and Coleoptera. These so-called Keimbahn- 

 determinants are located at the posterior end of the egg, as is the 

 case with the secondary yolk or parasites in Hemiptera, but are 

 known by several names. Thus Ritter ('11) gave the name of 

 'Keimwulst' for the Keimbahn determinants of Chironomus, 

 while Hasper ('11) termed them 'Keimbahnplasma.' . A similar 

 substance is described as 'Dotterplatte' in Calliphora (Kahle, 

 '08), but is called 'polares plasma' in Miaster (Hegner, '12). 

 Recently Hegner ('09) applied the term 'pole disc' to a related 

 substance in the eggs of chrysomelid beetles. The same nomen- 

 clature was adopted by Wieman ('10) two years later for an 

 allied species. 



The origin of the Keimbahn determinants in these insects is 

 still unknown. Hegner ('08, '10) states that he has attempted 

 to trace their origin, but failed to arrive at an exact source in the 

 case of the eggs of Chrysomelids (Hegner, '15). It was thought, 

 however, that as in the Hymenoptera chromatin granules might 

 be cast out of the nuclei of the oocytes, and that these granules 

 might gather at the posterior end to form the pole disc. It was 

 also suggested that chromatin granules from the nurse cell nuclei 

 might make their way into the oocyte and later become the 

 granules of the pole disc. It should not be forgotten, moreover, 

 that these granules stain like chromatin. In fact, they are non- 

 living substance and therefore cannot be homologous with the 

 simbiotic organisms found in Homoptera. There is, however, an 

 analogy in the relative position of these two kinds of polar in- 

 clusions, namely, the symbiotic organisms found in Homoptera 

 and the polar granules of eggs of Diptera and Coleoptera. The 

 germ cells of these insects become lodged in the polar granules 

 or symbiotic organisms early in the embryonic period. 



As to the function of the symbiotic organisms found in aphids 

 and coccids, very little can be said. As already stated, the germ 

 cells of coccids, before their migration into the colony of the 

 symbiotic organisms, are already differentiated. This excludes 



