Vol. XLI. October, 1921. .No. 4 



BIOLOGICAL BULLETIN 



ATTEMPTS TO CULTIVATE THE BACTEROIDS 

 OF THE BLATTIDAE. 1 



MARSHALL HERTIG. 



Since the discovery by Blochmann in 1887 of the bacteroids in 

 the fat-body and eggs of cockroaches, these organisms have been 

 studied by a number of investigators. The bacteroids are 

 organisms very closely resembling bacteria in theii morphology 

 and staining reactions. They are found in the fat-body of 

 roaches, filling the cytoplasm of certain cells, the bacteriocytes. 

 They are also found forming a layer over the surface of ovarian 

 eggs and in the yolk of the developing egg. They migrate from 

 the yolk into the fat cells of the half-grown embryo, where they 

 are found in older embryos, nymphs and adults. The bacteroids 

 have been found in all individuals of nine species of Blattidae thus 

 far studied, namely, Blatella germanica, Blatta orientalis, Ectobia 

 livida, Ectobia lapponica, Blabems sp., Periplaneta americana, 

 Periplaneta australasia, Parcoblatta virginica and Parcoblatta 

 pennsylvanica. No blattid is known to lack the bacteroids. 



The morphology and behavior of the bacteroids in the host 

 tissues are almost identical in all the species studied. The 

 relation of the bacteroids to the host is not understood. The 

 relationship may be merely one of harmless parasitism, there 

 being maintained a delicately adjusted equilibrium between host 

 and parasite, or it may be one of symbiosis, in which both 

 bacteroids and their carriers derive some benefit from the asso- 

 ciation. 



The striking morphological resemblance of the bacteroids to 

 ordinary bacteria and the fact that they multiply within the 

 body of the cockroach have led a number of workers to attempt 



1 Published with the approval of the Director, as Paper No. 246 of the Journal 

 Series of the Minnesota Agricultural Experiment Station. 



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