CHAPTER IV. 



VEGETATIVE REPKODUCTION BY FISSION. 



42. Division in One Direction. 



IN order to reproduce by fission in one direction, the cell becomes 

 elongated, and a partition (septum) is developed in the interior 

 of the cell at right angles to the length. This septum then 

 divides into two lamellae, thus effecting the separation of the 

 daughter-cell from the mother-cell. If the organism is living 

 under conditions favourable to its vitality, each of these cells will 

 soon undergo a similar process of division. In many instances 

 the new-formed cells of the second, third, fourth, &c., generations 

 do not become entirely detached, but remain connected one with 

 another; and if as is most often the case the division takes 

 place continuously in the same direction, chains of cells are 

 formed. When the members composing the chain consist of 

 cocci, the fission fungus is frequently designated a streptococcus, 

 instead of merely coccus. Hallier and Itzigsohn proposed to 

 apply the term Mycotlirix to these rosaries of cocci. When the 

 members are united chiefly or exclusively in pairs, the organism 

 is termed diplococcus ; and such of the cocci as incline to group 

 themselves in grape-like agglomerations are frequently designated, 

 in medico-bacteriological literature, by the name staphylococcus, 

 first bestowed on them by OGSTON (I.) in 1880. 



If the members of a chain are not iso-diametric cocci, but rods, 

 they are mostly termed thread (filamentous) cells, of which the 

 hay bacillus affords an excellent example. 



In an iso-diametric cell, the separation of the new cells and 

 therefore the preliminary expansion of the mother-cell may occur 

 in one of two directions : either lengthwise or crosswise, the 

 former case wherein the position of the dividing septum is 

 transverse, i.e. perpendicular to the longitudinal direction being 

 the most usual. On the other hand, only a few examples of the 

 second or longitudinal separation are as yet known. One of 

 them is afforded by the Bacillus tumescens, discovered by ZOPF (I.), 

 which will nearly always be found infesting slices of boiled carrot, 

 when the latter are left to themselves for some time in a not 

 too damp condition. According to the conditions of vitality pre- 

 vailing, this microbe develops either chains of long cells formed 

 by transverse fission, or cell bands the members of which are 



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