306 Prof. R. Boyce and Mr. A. E. Evans. 



the growth does not appear to be affected by any of the colours.. 

 Some of those who have seen our results think there is more growth 

 towards the blue end ; others, on the other hand, towards the red 

 end. We ourselves have come to no definite conclusion as yet. 



Microscopic Characters of the Cultures in the various Nutrient Media, 

 The series of photographs which illustrate these points have been 

 fixed and stained in the gelatine, as previously mentioned. We have 

 divided them into three groups. The first group, figs. 15 to 20, repre- 

 sent the filamentoiis phase of the early growth; fig. 17, for example, 

 representing the long segments observed in the rapidly growing- 

 pinnate filaments. Groups II and III quickly follow upon the first. 

 Group II, figs. 21 to 23, we venture to call the skein phase, which we 

 think corresponds to the etat enchevetre of Billet. Group III, figs. 24 

 31, we think represent the zob'glea phase. There yet remains a fourth 

 group, which we have not represented, and in which the segments 

 live an independent existence (as partly shown in fig. 18) and very 

 often are freely motile. We would call this the dissociated phase, the 

 etat dissocie of Billet. We have in this system of group phase division, 

 therefore, followed Billet.* Whether this is a reasonable method of 

 division will have to be judged from our photographs, from certain 

 peculiarities exhibited by the above-mentioned groups, and lastly 

 and chiefly from further examples. 



In figs. 15 and 16, Zeiss obj., mm. 75 without eyepiece, the original 

 streak of inoculation and the branches which spring from it are seen. 

 The streak presents interesting peculiarities. Very slight liquefac- 

 tion of the gelatine may be observed in it, and then very commonly 

 swarming obtains; as previously mentioned, the motile segments may 

 vary very greatly in length. In the figures in question clumps of 

 bacilli occupy the central streak. In some cases, however, long 

 zooglea-like twisted masses, like those seen in fig. 25, run straight 

 along this streak, it thus appearing as if their direction had been 

 determined by the inoculating needle. In other cases the central 

 streak is a mass of round zoogleaform. collections. It will be seen 

 that the micro-photographs in the first group afford very little evi- 

 dence of the negatively geotropic tendency of the filaments, only the 

 slight amount depicted in fig. 15 being often seen. The thicker 

 branches in figs. 15 and 16, and all the branches in figs. 24 and 25, 

 have assumed the zoogleaform condition. The microscopic picture 

 presented by the rapidly growing pinnate form differs very markedly 

 from, these ; in it nearly all the fibres in the field run parallel to one 

 another, the microscopic picture then quite coinciding with the 

 microscopic appearance seen, say, in fig. 1 or 14. In the pinnate 

 forms it is exceedingly difficult to trace the origin of the fibres in the 

 central line as well as to folloAv out the mode of branching ; this is 



* Loc. cit. 



