694 Journal of Agricultural Research voi.vi,No.i8 



(12), who is also of the opinion that some "copulative" process takes 

 place. 



In future publications we will have to give more illustrations showing 

 the different forms of the various kinds of regenerative bodies produced 

 either directly by the different bacteria or by their symplasms. It seems 

 as if such irregular, sometimes monstrous-looking formations as repro- 

 duced, for example, in figure 26 (PI. E), are very constant and very 

 characteristic for the species to which they belong. This is already well 

 known in the case of B. radicicola, and our figures 37 and 38 of Plate G 

 may demonstrate the same fact in relation to Micrococcus candicans. The 

 preparates were made from 6-day-old cultures in an ammonium-citrate 

 solution. One strain (No. 44) had been isolated about six years ago 

 from Russian black soil; the other (No. 45) nine years ago from evap- 

 orated milk. The characteristic appearance, as well as the uniformity 

 of both illustrations, deserves our full attention. 



Figures 39 and 40 (PI. G) show the formation of well-stained gonidia 

 by the yellow bacillus (No. 41) and by B. fluorescens (No. 40). In both 

 cases the transformation of gonidia into regenerative bodies is clearly 

 visible (cf. fig. 29 of PI. E). Figure 39 (PI. G) contains also in its lower 

 left quarter some germinating regenerative bodies. The "budding" 

 process is very conspicuous in this case, but the second picture makes it 

 clear that the size of the gonidia frequently becomes so small that even 

 a very careful observation of the stained preparate is hardly of any use. 

 Besides, as many of these gonidia do not take the stain at all, some 

 filtering experiments and the observation in the dark field seemed to 

 be preferable. 



FORMATION OF FILTERABLE GONIDIA 



The formation of gonidia has been observed with all our different cul- 

 tures, but whenever we saw a large number of gonidia in our preparates, 

 there were always some, frequently many, just at the limit of visibility. 

 It was to be expected that these would pass through Chamberland 

 bougies. As our other experiments had shown that these gonidia are 

 indeed living entities, some tests seemed to be of interest, especially in 

 view of the many open questions concerning the occurrence and character 

 of filterable vira. 



The following cultures were used for making filtering tests : 



No. 1 (B. azotobacter) , 24 days old in a mannite-nitrate solution; No. 31 

 (B. subtilis), n days old, in ammonium-citrate-glycerin solution; No. 33 

 (Tyroihrix tenuis), No. 35 {Bad. pneumoniae), and No. 40 (Bact. fluores- 

 cens), each from a 2-day-old culture in ammonium-citrate-glycerin 

 solution. 



The filtrates were first tested under the microscope. Stained prepa- 

 rates had to show the absence of large forms. By the use of the dark 

 field the small gonidia could easily be seen, some of them being actively 



