Jennings — 0)i a Ncto Genus of Bacteria (Astrobacter) . 315 



the theory of longitudinal fission is a relatively slight strain on the 

 scientific imagination. 



We have to consider in the first case whether snch longitudinal 

 fission is improhahle, and, in the second, what evidence is derivable 

 from other forms of life. 



If we accept the view of the physiological necessity for division at 

 the limit of growth there is no difficulty ; because though there might 

 be greater expenditure of energy in longitudinal than in transverse 

 division there would be proportionately greater gain in new surface- 

 area. This, it seems to me, holds true whatever opinion may prevail 

 as to the ultimate meaning of cell-division. 



No theoretical objection, however, can be of much value if the 

 phenomenon actually occurs in other organisms ; and such forms as 

 Gomphonema and Licmophora among the Diatomacese, and those 

 Infusoria which divide to form fan-shaped and radial colonies, show 

 that there is nothing impossible in the idea. The multiplication of the 

 cells in primitive columnar epithelia may be analogous. 



This view would have been put forward with greater hesitation had 

 it not been for the fact that one form of Schizomycete has already beer 

 described which shows similar longitudinal division. In the Annals oi 

 the Pasteur Institute, Metschnikoff has called attention to a curious 

 organism which consists of radiating groups of pear-shaped cells. 

 These he regarded as produced by longitudinal fission from a simple 

 form, and gave generic value to the type under the name of Pasteuria. 



Taking these facts into consideration, as well as the tendency to 

 radial differentiation of the cell-protoplasm seen in the Radiolaria, 

 or in the embryo discs of an alga like Phycopeltis, one might hazard 

 the suggestion that, while both in unicellular organisms and in tissues 

 the transverse type of fission generally prevails, there are some cases 

 in which an archaic tendency to longitudinal or radial division still 

 predominates. 



If future observation proves the occurrence of longitudinal division 

 in this case or in Pasteuria, it may be convenient to separate these 

 forms in a section of Schizomycetes termed" Paraschizse" in antithesis 

 to a section of " Diaschizse " which would include the better known 

 bacteria. 



I am, however, by no means sure that there is any fundamental 

 difference between the two types of division ; and if I have seemed to 

 emphasize the distinction, it is because, when a preliminary note on this 

 ■organism was communicated to the Botanical Section of the British 



