PHILIP HADLEY 91 



cluster of nucleus-like granules. Mellon has also recorded the liberation of large numbers of 

 minute and apparently motile granules from the "giant coccus" forms. This has also been 

 reported by Kuhn/ who has presented beautiful micro-photographs of these cells (Petten- 

 kofer bodies) both before and after the liberation of the minute granular bodies. From his 

 work it appears that these small forms often fail to stain by the ordinary methods, but that 

 the Giemsa stain is especially favorable. It may be added at this point that Kuhn sees a 

 relation between the presence of these bodies and the ability of the culture containing them 

 to generate the bacteriophage; and this is quite in harmony with the theory of transmissible 

 autolysis which I have proposed in an earlier paper. 



Regarding the development of the zygospores, Mellon has observed that in some cases 

 they appear to undergo a double segmentation and yield a large coccus form like that often 

 encountered in dissociating cu tures of B. diphthcriae. In such instances Mellon regards the 

 zygospores as transition Anlagen for the development of a new form of culture, the exact 

 nature of which will be determined by the environment surrounding the germinating zygo- 

 spores. 



Finally, with reference to the hereditary mechanism of bacteria, there should be 

 mentioned the formation of symplastic structures such as those first described by 

 Jones^ in 1913 and 1920 for Azotobacter, and confirmed by both Lohnis-* and Ender- 

 lein.'' Briefly, the reaction involves the fusion of a mass of bacteria into a single group 

 in which the cell boundaries are lost and a union of nuclear elements occurs. From 

 such symplastic structures arise new individual cells. 



THE CULTURAL APPROACH 



As early as 1888 observations dealing with several different and more or less per- 

 manent culture types arising from pure cultures had been described by Firtsch^ for 

 V. proteus, and in 1895 Dyar^ gave a report on changes of a somewhat similar nature 

 for B. lactis erythrogenes. In later years other investigators presented other instances 

 in which striking departures arose from the long-assumed "normal" and constant 

 type. Many of these instances we owe to the splendid researches of Eisenberg.'^ It re- 

 mained for Baerthlein,* however, in 1918 to point out the frequent occurence of such 

 variations, their cultural, biochemical, and — to a limited extent — serological reactions. 

 The primary basis for Baerthlein's important study was colony variation, the signifi- 

 cance of which had been clearly seen by Firtsch in the case of a single species, Baerth- 

 lein showed that plating from old laboratory cultures commonly resulted in the ap- 

 pearance of colony forms quite unlike that of the original culture. Sometimes only 

 one or two colony variants were encountered; at other times, four or five of them. But 

 the most important and significant feature of Baerthlein's study was his demonstra- 

 tion that, commonly associated with colony variation, were variations in other char- 

 acteristics — morphological, biochemical, and serological. 



' Kuhn, Philaethes: loc. cit. 



^ Jones, D. H.: loc. cit. 



3 Lohnis, F. : loc. cit. 



'' Enderlein, G.: Bakterien-Cyclogenie. Berlin, 1925. 



5 Firtsch, G.: Arch.f.Hyg.,8,s(>g. 1888. 



^Dyar, H. G.: Ann. N. Y. Acad. Med., 8, 322. 1895. 



' See Hadley, Philip: loc. cit. ^ Baerthlein, K.: ibid., 81, 369. 1918. 



