BIOLOGICAL STUDIES ON INTRACELLULAR 

 BACTERIA. 1 NO. i. 



R. W. GLASER. 



INTRODUCTION. 



It has been known for a long time that certain blattids, homop- 

 tera, and ants harbor intracellular non-pathogenic organisms that 

 are transmitted from generation to generation through the egg. 

 Since Huxley's description of the pseudovitellus of aphids in 

 1858 a host of investigators have studied the embryonic develop- 

 ment and morphology of this curious organ and its contents. 

 After Huxley, the most prominent investigators associated with 

 the study of this subject and with the development of the entire 

 field oi intracellular organisms in insects, were Lubbock, Metchni- 

 koff, Balbiani, Krassilstschick, Blochmann, Lindner, Heymons, 

 Berlese, Mercier, Pierantoni, Sulc, Buchner and others. 



This vast study has precipitated the following facts and theories 

 which may be presented seriatim. 



1. The insects that are definitely known to harbor intracellular 

 non-pathogenic organisms belong to the family Blattidse, the 

 entire order of Homoptera, and the family Formicidse. 



2. It has also been reported that certain Lepidoptera and Cole- 

 optera harbor intracellular non-pathogenic organisms, but con- 

 ditions are not clear in the cases cited and the authors may have 

 been confronted with true pathologic cases. 



3. In the insects where non-pathogenic intracellular residents 

 have been established one or more definite species of micro- 

 organisms are always associated with every individual of a par- 

 ticular species of host. 



4. The microorganisms associated with the insects have been 

 called symbionts. 



5. The symbionts are transmitted from generation to genera- 

 tion through the egg in a very definite manner. 



i Contribution from the Entomological Laboratories of the Bussey Institu- 

 tion, Harvard University. Bussey Institution No. 174. 



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