1880.] Dr. G. Thin. On Bacterium foetidum. 



475 



various forms with each other, and thus tracing the successive stages 

 in the development. 



Examples of these different stages were drawn (Plate 6), and with 

 the assistance of the figures I shall endeavour to describe what I 

 believe to be the order of succession. 



The first stage is undoubtedly the production of a pair from a single 

 coccus. The individuals of the pair were sometimes found so closely 

 associated that there was no independent movement in each member, 

 in some a distinct movement of each could be observed, whilst in others 

 the union was so loose that there was a perceptible distance between 

 them, and they oscillated round each other, connected undoubtedly by 

 a baud of union which with the microscope I employed was not dis- 

 tinctly visible. 



The next stage I take to be that in which the whole body is wedge- 

 shaped, the round brightly refractive coccus being found in the thick 

 end of the wedge. Another phase which is probably the successor of 

 the preceding one, is the appearance of a canoe-shaped figure with the 

 bright coccus in the centre. In one of these canoe-shaped bodies 

 Mr. Knowsley Thornton and myself observed two of the bright refrac- 

 tive bodies in active oscillation in the centre of the canoe ; one and 

 then two being successively visible according to their relative position. 

 The canoe-shaped envelope itself was motionless (the preparation was 

 a permanent one sealed in diluted Groadby's solution), and Mr. 

 Thornton was able to draw it with the camera. (See fig. 2, a, b.) 



Other appearances connected with the early stage of development, 

 and probably following the wedge and canoe-shaped figures, show the 

 organism developed into a staff-shaped body, containing two elements 

 of very different refractive power. The coccus element is still distinct 

 and is brightly refractive, the other element is very slightly refractive 

 and is seen as a dull shade, with however perfectly distinct outlines. 



The latter element it may be convenient to term protoplasm, using 

 the word merely to express the idea of an element which is distinct 

 from the coccus and the sheath. The relative positions of the coccus 

 or cocci and the protoplasm are various. 



The coccus may be at one end of the rod, two cocci may be in the 

 centre close together with a prolongation of protoplasm on either side, 

 or a central rod of protoplasm may have a coccus at either end. 

 (Fig. 2.) 



In the next stage we have the formation of the rods characteristic 

 of bacteria. The distinction between the coccus and the protoplasm 

 becomes lost, although transitions are found in which faint differences 

 of refraction still betray the two elements. At this stage, in the 

 double flail-shaped rods, the one member sometimes refracts differently 

 from the other, the development being evidently in a different stage. 

 The numerous two-, three-, and four-jointed rods attached to each 



