ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 591 



propagated bj implantations of sick animals among healthy populations. 

 'She employment of d'Herelle's technique should be used in conjunc- 

 tion with other methods of locnst destruction. 



Life-cycles of the Bacteria.* — E. Lohnis and N. R. Smith con- 

 tribute, as a " Preliminary Communication," an important memoir on 

 this subject, chiefly based on the study of the life-history of Bacillus 

 azotobacter, in which they show that the life-cycles of the bacteria 

 are no less complicated than those of many other micro-organisms. A 

 satisfactory account of the development of one form of this species from 

 another would be too lengthy, and would require the reproduction of 

 a complicated page diagram, but it may be stated that all bacteria studied 

 have been found to live alternately in an organized and in an amorphous 

 stage, from which stage in all cases •' regenerative units " develop, and, 

 increasing in size, turn into " regenerative bodies," which later become 

 cells of normal shape. Direct union of two or more individual cells has 

 also been observed. All bacteria are found to multiply not only by 

 fission, but also by the formation of "gonidia," which usually first 

 become regenerative bodies, but sometimes directly grow to full-sized 

 cells. The gonidia are liberated either by complete or partial dissolution 

 of the cell-wall, or they develop while still united with their mother-cell. 



The authors state that the discovery of the full life-cycles of the 

 bacteria may be useful in many ways ; for the wide morphological 

 variations are connected with great variations in the physiological 

 qualities of the organisms ; many so-called species will have to be 

 cancelled, because they merely represent fragments of the life-cycles of 

 other bacteria ; systematic bacteriology can now be established on a firm 

 experimental basis ; and medical bacteriology as well as agricultural 

 will derive much benefit. 



The seven plates are collotype reproductions of forty-two micro- 

 photographs of various species of bacteria in different stages and of their 

 gonidia. 



Bacteria in Bottled Waters.t — Maud Mason Obst gives the results 

 of a bacteriological examination of commercial bottled waters, from 

 which the conclusion is drawn that insufficient care is often exercised in 

 the selection of the spring from which the water is obtained, and after- 

 wards in handling the water. It was found that naturally carbonated 

 waters occasionally contain large numbers of organisms, but that arti- 

 ficially carljonated waters generally contain very few, Bacillus coli being 

 almost entirely absent. The results of an examination of two imported 

 waters, bearing on the labels of the bottles " bacteriologically pure," are 

 of interest. Out of six bottles in one sample, four contained B. coli iu 

 varying and sometimes possibly harmful quantities ; and out of seven in 

 the other sample, six did so, besides which thirteen other species were 

 detected, and long-chain streptococci, also moulds of the genera Tricho- 

 dermu, PeniriUium, Gitromyces, Fusnriion, Actinomyces^ and Sporofrickum. 

 One imported water examined contained a large number of spores of a 



* -Jouru. Agric. ResGcarch, Washington, vi. pp. 675-702 (pis. A-G). 

 t U.S. Dept. of Agriculture, Bull. No. 369 (1916) 14 pp. 



