Jennings — On a New Genus of Bacteria (Astrobacter) . 313 



is a similar rod bifurcated at the end, producing- a Y-shaped form 

 (PI. VII. figs. 2, 3) ; and, apparently as a further development of this, 

 come symmetrical tri-radiate types, "with the rays spreading at an 

 angle of 120° (PI. YII. fig. 4). 



These simple Y-shaped specimens seem to me imdouhtedly due 

 to the longitudinal splitting of the simple rod, and they thus give 

 an explanation of the more complex stars for which it would other- 

 wise be difiicult or impossible to account. 



It is, of course, true that if a simple bacterium develops a 

 lateral branch, a Y-shaped form will result when the side branch 

 equals in length the shorter portion of the original rod. In the 

 present case the branches of the fork are always equal, and some 

 special stress may, perhaps, be laid upon this point, because when 

 these specimens came under my notice, I was studying Mr. Coppen 

 Jones' preparations, illustrating the branching of the " Tubercle 

 Bacillus." In that organism I was able to observe the branching 

 of a simple rod-like form, and to trace this stage into the more com- 

 plex " hyphal " condition which he has described.*'' It is not likely, 

 therefore, that in the present case I should have been misled by 

 mere lateral outgrowth. 



To return, however, to description : — Four-rayed forms, with 

 acute and obtuse angles between the pairs of rays (PI. YII. figs. 5, 6), 

 are not uncommon, and all transitions may be found from this type 

 to a regular cruciate such as that of fig. 7. Then come five-rayed 

 examples, again showing much variation in the angle between 

 adjacent rays ; and then hexactinellid forms, irregular in some cases, 

 in others as symmetric as a simple snow-crystal (PI. VII. figs. 8-10). 



Of the more complicated specimens those with eight-rays are 

 also often symmetrical, but those with more than eight are almost 

 always irregular in the length and disposition of the rays (PL VI. 

 fig. 2; PL VII. figs. 12-17). 



A zoologist examining the specimens will be struck by the 

 curious parallelism between these different growth-forms and the 

 various types of spicules in sponges. We have forms correspond- 

 ing to the simple rods and triradiates ; the four-rayed type ; the 

 tetraxonoids ; the symmetrical hexactinellid form of a Hyalonema, 

 and the irregular multiradiates of some fossil genera. 



The comparison of the two series is merely one that suggests itself, 

 unavoidably, in looking at the specimens. Still, there may be some 



^ Coppen-Jones — CentralLlatt fur Baeteiiologie 1895. 



