June, '34] burn side: bacteria associated with European toulbrood 667 



their thickness, shorter rods, coccoid cells, and lancet-shaped cells were 

 observed in the same chains in broth cultures of 5". apis. In cultures on 

 bouillon agar to which 10 per cent honey was added, some of the cells 

 were increased in size, many were distinctly rod-shaped, while others 

 assumed lancet shapes indistinguishable from B ' alvei ( Plate 6, L ) . 

 In broth cultures of 5'. apis containing both honey and unheated egg 

 yolk, several variants were observed after 2 days, including large, irregu- 

 lar, barrel-shaped, and spherical cells, occurring usually in pairs or 

 in chains. 



Conclusions. — Several morphologically different bacteria forms are 

 more or less constantly present in honeybee larvae sick or dead of 

 European foulbrood. These forms are absent in larvae sick or dead of 

 other causes. 



No evidence has yet been obtained which satisfactorily explains the 

 etiology of European foulbrood or why these different bacterial forms 

 are constantly associated with this disease. 



It has been found that Bacillus alvei is capable of morphological, cul- 

 tural, and biological transformation and is also capable of stabilization, 

 at least temporarily, as a sporogenic rod, an asporogenic rod resembling 

 Bacterium eurydice, or a coccoid resembling Bacillus pluton. 



There seems to be insufficient reason for assuming that the lancet- 

 shaped bacterial cell, B. pluton, found in late stages of infection in 

 European foulbrood, is of different genus and species from the similar 

 form Streptococcus apis, which is readily obtained in culture from sick 

 larvae. 



The identity of Streptococcus apis and Bacillus pluton is suggested by 

 morphological similarity, by the fact that the pointed or lancet shape is 

 a variable character in both forms and appears to be only an expression 

 of restricted growth or dormancy accentuated in infected larvae, and 

 also by the usual, if not invariable, occurrence of Streptococcus apis in 

 recently infected larvae, and by the fact that typical European foul- 

 brood was produced in Wharton's and in the writer's experiments when 

 young brood was inoculated with cultures of 6". apis prepared with 

 isolated colonies. 



That Bacillus pluton and Streptococcus apis are variants, or stages in 

 the life history, of Bacillus alvei is suggested by the occurrence of vari- 

 ants resembling B. pluton in pure cultures of B. alvei and by the apparent 

 origin on rare occasions of sporogenic B. alvei in cultures 5. apis. 



The transformation at room temperature of sporogenic B. alvei into 

 an asporogenic nonmotile rod which morphologically, culturally, and bio- 



