172 CLASSIFICATION OF THE MICRO-OfcGANIbAIS. 



not distinctly marked when the act of fission has 

 begun, and while the two cells still adhere to one 

 another and the constriction is incomplete (diplococcus) . 

 The cells which are undergoing division are under 

 these circumstances elongated with a sharp and more 

 or less deep constriction in the centre, so that they 

 resemble a short rod. A comparison with neighbour- 

 ing individuals not yet undergoing division, or with 

 those in which the division has proceeded further and 

 led to distinct formation of two spheres, is as a rule 

 sufficient in such a case to enable the diagnosis to be 

 made as against bacilli. After the division is complete, 

 the micrococci either remain isolated or they assume 

 short bacill:-. the various arrangements mentioned on page 156, 

 staphylococcus, streptococcus, merismopedia, sarcina, 

 zooglsea. If in the zooglaea formation the intercellular 

 substance is very tough, so that cartilaginous masses are 

 formed enclosed in the general mass, the group is termed 

 ascococcus; if the gelatinous masses of such groups 

 become dissolved in the interior, so that only a thin ex- 

 ternal layer surrounds a hollow cavity filled with fluid, 

 the arrangement is termed clathrocystis. 



Distinction 



DIVISION 2. BACILLI. 

 Morphological Rods in which the longitudinal diameter is 2, 3, or 



characters of ... f , , m-i 



the bacilli. many times in excess of the transverse. The organ- 

 isms belonging to the class of the bacilli for the most part 

 pass through a definite cycle of forms, so that they do 

 not appear exclusively in the vegetative form, bacillus ; 

 many can form threads, and in these spores ; in others 

 there is only well-marked thread formation ; others pro- 

 duce spores in their middle, at the end, or at several 

 places, according to the modes described on p. 161 ; most 

 of them form at times all sorts of involution forms. 

 We may also meet with these bacteria under many 

 different forms ; but it is characteristic for all the thread 

 forms, and round or oval cells, occurring in connection 

 with the bacilli, that they have been developed from 

 cells having the vegetative form of bacillus, and that if 



