E. Ray. Lankester

ABSTRACT It is now five-and-twenty years since Professor Lankester first undertook the task of editing the ‘Quarterly Journal of Microscopical Science/ and by issuing the present number his colleagues desire to mark the occasion, and at the same time to take the opportunity of offering to him their hearty congratulations on the success which has attended this quarter of a century of effort on his part. Since the classical papers on Bacteria published by Professor F. Cohn in the ‘Zeitschrift der Biologie d. Pflanzen,’ vols, i to iii, all bacteriologists have accepted the subdivision of the Schizomycetes into cocci, bacilli, and vibrios or spirilla, as representing the main morphological fundamental types. But by Lankester1 and Zopfs’researches on Cladothrix dichotoma, and by Hauser’s well-known and exhaustive work on ‘Putrefactive Bacteria’ (‘Ueber Fäulnissbacterien,’ Leipzig, 1885), it has become recognised that the shape under which a particular bacterial species presents itself depends both on the medium in which it grows, as also on certain inherent characters of the organism itself. Thus it has become recognised that while the elements of one species appear as often in the form of oval as of cylindrical cells, those of another retain, under almost all conditions, pre-eminently that of cylindrical cells. To name a few instances : (a) the Proteus vulgaris of Hauser. This organism—the organism of putrefaction par excellence—is known to occur in the most varied shapes, as cocci, oval forms, cylindrical and vibrionic forms; but when growing in gelatine plates at 20° C. it will be found that in the first twenty-four to forty-eight hours the colonies are made up entirely of cylindrical bacilli, some of extreme length and forming very characteristic threads. The “swarming” out and the development of strands from such a colony are uniformly due to, and consist of, thread-like bacilli (see my article in Stevenson and Murphy’s ‘Treatise on Hygiene,’ II, pl. ii) ; but later on, say after three or four days, when liquefaction of the gelatine has become extensive, the forms one meets are those various kinds described by Hauser as coccus forms, ovals, cylindrical cells, and vibrionic forms.