PAUL F. CLARK 39 



physiologists, and have tended to minimize the importance of morphological studies. 

 And if unusual forms are seen, what can be easier than to assume that these are 

 mutants, involution forms, or contaminations? 



In spite of this tendency to stress uniformity, the variability of bacteria has forced 

 its way through our methods so that a number of men have been led to make careful 

 cytological observations and eventually to take a position diametrically opposed to 

 the concept of fixed morphology. The work of Nakanishi,' Schaudinn,^ Grimme,^ 

 Mencl,"* GuilliermondjS Ambroz,** Dobell,' Lohnis,* Hort,' Mellon,'" Bergstrand," En- 

 derlein," Kirchensteins,''^ Thornton and Gangulee,''' and Cunningham and Jenkins,'^ 

 to name only a few, has been especially noteworthy. It has given foundation for the 

 opinion in the minds of some bacteriologists that bacteria are not simple structureless 

 cells, but fungi with formed nuclei, some of them showing mitotic division and com- 

 plex life-cycles. Since this conception is philosophically attractive and would co-or- 

 dinate bacteria more closely with the rest of the biological world, it is easier for some 

 to accept the evidence as adequate, while others feel that this attractive prospect is 

 an additional reason for maintaining a position of unusually strict skepticism. 



The existence of a formed nucleus even in the simpler bacteria (Eubacteriales) has 

 been demonstrated beyond doubt especially by Nakanishi,'* Dobell,'? Guilliermond,'* 

 Meyer,'' Mencl,^" and Kirchensteins.^' By different technique, with material from 

 a variety of sources, in organisms from young and old cultures, in both the simpler 

 and the higher bacteria, spore-formers and non-spore-formers, nuclei have been dem- 

 onstrated. The form of the nucleus is variable not only in different species, but also 

 in different stages of the development of one species. In cocci the nucleus is usually 

 more or less spherical, and in fission begins to divide before the division of the cyto- 

 plasm. In rods and spirilla the nucleus is more variable and may be seen in the form 



' Nakanishi, K.: Munchen. -wed. Wchnschr., 47, 187. 1900; Centralbl.f. BakterioL, Abt. I, 30, 97, 

 145, 193, 225. 1901. 



^ Schaudinn, F.: Arch. Prolistenk., 2, 421. 1903. 



3 Grimrae, A.: Centralbl.f. BakterioL, Abt. I, 32, i. 1902. 



'• Mencl, E.: Arch. Prolistenk., 8, 259. 1907. 



5 Guilliermond, A.: Bull. Inst. Pasteur, s, 273, 321. 1907. 



*Ambroz, A.: Centralbl.f. BakterioL, Abt. I, 51, 193. 1909. 



'Dobell, C. C: Quart. J. Micr. Sc, 56, 395. 1910-11. 



'Lohnis, F.: Mem. Nat. Acad. Sci., 16, i. 1921. 



9}iort,E.C.: Proc. Roy. Soc.,'B, 8g, 468. 1917; 5n7. M. /., i, 571, 664. 1917; j&i(/., 2,377. 1917; 

 J. Roy. Micr. Soc, 365. 191 7; J. Hyg., 18, 361. 1920; ibid., p. 380. 1920. 

 '"Mellon, R. R.: Am. J. M. Sc, 159, 874. 1920. 

 " Bergstrand, H.: /. Bad., 8, 365. 1923. 

 '^ Enderlein, G.: Bakterienzyklogenie. Berlin, 1925. 



'3 Kirchensteins, A.: Structure interieure et Mode de Develop pement des Bacteries. Riga, 1922. 

 "•Thornton, H. G., and Gangulee, N.: Proc. Roy. Soc, B, 99, 427. 1926. 

 '5 Cunningham, A., and Jenkins, H.: /. Agric Sc, Part I, 17, 109. 1927. 

 '^ Nakanishi, K.: loc cit. ^^ Dobell, C. C.: loc. cit. '* Guilliermond, A.: loc cit. 



'"Meyer, A.: C&ntralbl.f. BakterioL, Abt. II, 6, 339. 1900. 

 '0 Mencl, E.: loc. cit. ^' Kirchensteins, iK.: loc. cit. 



